diff --git a/Day_5/Day_5.jl b/Day_5/Day_5.jl
new file mode 100644
index 0000000..a60bf2a
--- /dev/null
+++ b/Day_5/Day_5.jl
@@ -0,0 +1,469 @@
+### A Pluto.jl notebook ###
+# v0.18.4
+
+using Markdown
+using InteractiveUtils
+
+# ╔═╡ c7e76680-571e-427d-a564-8819df8b3750
+# Oh, no, you found my secret! 😱
+# Don't change this hidden cell!
+begin
+	using PlutoUI
+	
+	TableOfContents()
+end
+
+# ╔═╡ c7256818-f2ab-4f8a-be6f-1d2c97dca981
+md"""
+# Structs
+Julia as a functional language does not have classes like in object oriented languages. Instead, Julia has structs.
+
+Using structs, you can define your own types. Structs use type composition. This means that you combine types into a new one.
+
+In Julia, type annotations DO NOT lead to any performance boosts. Structs build an exception! If you are writing a struct, you have to use type annotations with concrete types (not abstract)!
+"""
+
+# ╔═╡ 3e3e324d-5650-4f81-87cf-fb0f6f55d9d1
+struct Vec2d
+	x::Float64
+	y::Float64
+end
+
+# ╔═╡ 2ab6f97f-8eed-4b86-9eb6-1de88e6c846d
+vec_2d = Vec2d(1.0, 1.0)
+
+# ╔═╡ 377a9100-efd8-479c-b9f6-68584c886800
+typeof(vec_2d)
+
+# ╔═╡ 0e62a7b2-0636-4018-b005-0ae674fec45e
+# Wow, we did reach infinity ♾️
+Vec2d(factorial(big(1000)), 2.0)
+
+# ╔═╡ 6046417c-460b-4b0c-8423-4d6c4c18731f
+struct BadVec2d
+	x::Real
+	y::Real
+end
+
+# ╔═╡ 3e21d34f-3758-427f-85c0-7c457f3f0904
+bad_vec2d = BadVec2d(factorial(big(1000)), 2.0)
+
+# ╔═╡ 4a07f5e3-2413-49c4-824c-b9c844695052
+typeof(bad_vec2d)
+
+# ╔═╡ 9008b1c4-ad76-4d4f-b6c5-001a77543b97
+struct BetterVec2d{T<:Real}
+	x::T
+	y::T
+end
+
+# ╔═╡ 830dd737-4fdc-42c7-b105-d0622b055db1
+big_vec2d = BetterVec2d(factorial(big(1000)), big(1))
+
+# ╔═╡ f91b0c58-bc44-414a-b357-145d8c4339d2
+typeof(big_vec2d)
+
+# ╔═╡ 3f1b8df9-104b-42c3-97ee-11782f9f744f
+# BetterVec2d(1.0, 1)
+
+# ╔═╡ 10c380fd-80e6-4cb7-b50e-1a7998ec00c5
+abstract type Student end
+
+# ╔═╡ 58de483d-c2b5-4252-b6da-64bd8bfac1ac
+struct MathStudent<:Student
+	name::String
+	hobby::String
+end
+
+# ╔═╡ 4024358d-f673-45f1-a12a-00a5554622e3
+struct PhysicsStudent<:Student
+	name::String
+	hobby::String
+	favorite_particle::String
+end
+
+# ╔═╡ b535fd1d-695d-49fb-8a6a-2f2f0053a6f6
+function print_name(student::Student)
+	println(student.name)
+
+	return
+end
+
+# ╔═╡ 63f32169-b98c-4212-bbd9-4c601266f209
+function print_information(math_student::MathStudent)
+	println("Math student: $(math_student.name)")
+	println("hobby: $(math_student.hobby)")
+
+	return
+end
+
+# ╔═╡ cb49717b-0584-430e-a30c-c4d02cf55eb2
+function print_information(physics_student::PhysicsStudent)
+	println("Physics student: $(physics_student.name)")
+	println("hobby: $(physics_student.hobby)")
+	println("Favorite particle: $(physics_student.favorite_particle)")
+
+	return
+end
+
+# ╔═╡ be428fea-fd34-4a08-94d2-c23ba0ecc586
+math_student = MathStudent("Felix", "Proofing stuff")
+
+# ╔═╡ da805692-8bf4-4eb5-a4ef-5a068c8a503b
+physics_student = PhysicsStudent("Robert", "Using harmonic oscillators", "Photon")
+
+# ╔═╡ 268904d5-6252-4ff7-9d8b-315b73736cac
+print_name(math_student)
+
+# ╔═╡ bc43e76c-3a9b-4f3f-9f88-28f2f7f868d1
+print_name(physics_student)
+
+# ╔═╡ 0a2619e4-9eed-4eb3-a411-c616ee840062
+print_information(math_student)
+
+# ╔═╡ bc8ef92b-1c68-4c9d-948a-6196dcd2b378
+print_information(physics_student)
+
+# ╔═╡ d8a2ae5c-b42a-4673-9a95-24cfc69ea3e7
+md"""
+# Writing documentation
+
+"""
+
+# ╔═╡ c24c04e4-b131-11ec-2c1b-7de12fe0c324
+md"""
+# Ecosystem
+In this section, some interessting Julia packages will be presented briefly. If you want to learn more about them, check out their documentation!
+"""
+
+# ╔═╡ 279d81e7-77d5-4855-bf45-a1a613265f65
+md"""
+## `PhysicalConstants.jl`
+"""
+
+# ╔═╡ 62e2481a-3fa1-4f2f-a7b6-7879c675701d
+md"""
+## `PeriodicTable.jl`
+"""
+
+# ╔═╡ aa40dc25-6355-45be-b577-c5a8a28f1a8a
+md"""
+## `PrettyTables.jl`
+"""
+
+# ╔═╡ 1ef034c9-da8d-4b35-8a98-532793b03718
+md"""
+## `GuadGK.jl`
+"""
+
+# ╔═╡ e80c4d19-d746-4ab8-88e0-2389a722edb6
+md"""
+## Makie
+"""
+
+# ╔═╡ 724f3fb4-1e49-4d58-a490-39d1110ba18c
+md"""
+### `CairoMakie.jl`
+`LaTeXStrings.jl`
+"""
+
+# ╔═╡ 431ffe1d-9e90-4344-ba35-0a5375954c0a
+md"""
+### `GLMakie.jl`
+"""
+
+# ╔═╡ eb836cdc-de12-430c-a6f3-1524ebd28865
+md"""
+## `JLD2.jl`
+"""
+
+# ╔═╡ 7e75da58-f110-41cb-ab19-79376370965f
+md"""
+## `Luxor.jl`
+"""
+
+# ╔═╡ 6b417e5d-01c2-4b06-9708-62c422a6b64b
+md"""
+## `DifferentialEquations.jl`
+"""
+
+# ╔═╡ b621819d-6ce3-41e1-9e61-3ad0a2c9b016
+md"""
+## `Intervals.jl`
+"""
+
+# ╔═╡ 0174178f-3ed9-4890-8482-714cb51a635d
+md"""
+## `ProgressMeter.jl`
+"""
+
+# ╔═╡ d29338b3-3c25-4ae4-90d0-1176538c635e
+md"""
+## `NaturallyUnitful.jl`
+"""
+
+# ╔═╡ 2430f309-be28-4bc2-9692-92489c31f7b2
+md"""
+# Resources
+
+"""
+
+# ╔═╡ 00000000-0000-0000-0000-000000000001
+PLUTO_PROJECT_TOML_CONTENTS = """
+[deps]
+PlutoUI = "7f904dfe-b85e-4ff6-b463-dae2292396a8"
+
+[compat]
+PlutoUI = "~0.7.38"
+"""
+
+# ╔═╡ 00000000-0000-0000-0000-000000000002
+PLUTO_MANIFEST_TOML_CONTENTS = """
+# This file is machine-generated - editing it directly is not advised
+
+julia_version = "1.7.2"
+manifest_format = "2.0"
+
+[[deps.AbstractPlutoDingetjes]]
+deps = ["Pkg"]
+git-tree-sha1 = "8eaf9f1b4921132a4cff3f36a1d9ba923b14a481"
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+
+[[deps.ArgTools]]
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+[[deps.Artifacts]]
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+
+[[deps.Base64]]
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+
+[[deps.ColorTypes]]
+deps = ["FixedPointNumbers", "Random"]
+git-tree-sha1 = "024fe24d83e4a5bf5fc80501a314ce0d1aa35597"
+uuid = "3da002f7-5984-5a60-b8a6-cbb66c0b333f"
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+
+[[deps.CompilerSupportLibraries_jll]]
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+
+[[deps.Dates]]
+deps = ["Printf"]
+uuid = "ade2ca70-3891-5945-98fb-dc099432e06a"
+
+[[deps.Downloads]]
+deps = ["ArgTools", "LibCURL", "NetworkOptions"]
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+[[deps.FixedPointNumbers]]
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+[[deps.JSON]]
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+
+[[deps.LibCURL_jll]]
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+uuid = "deac9b47-8bc7-5906-a0fe-35ac56dc84c0"
+
+[[deps.LibGit2]]
+deps = ["Base64", "NetworkOptions", "Printf", "SHA"]
+uuid = "76f85450-5226-5b5a-8eaa-529ad045b433"
+
+[[deps.LibSSH2_jll]]
+deps = ["Artifacts", "Libdl", "MbedTLS_jll"]
+uuid = "29816b5a-b9ab-546f-933c-edad1886dfa8"
+
+[[deps.Libdl]]
+uuid = "8f399da3-3557-5675-b5ff-fb832c97cbdb"
+
+[[deps.LinearAlgebra]]
+deps = ["Libdl", "libblastrampoline_jll"]
+uuid = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
+
+[[deps.Logging]]
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+[[deps.Markdown]]
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+
+[[deps.MbedTLS_jll]]
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+
+[[deps.Mmap]]
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+
+[[deps.MozillaCACerts_jll]]
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+
+[[deps.NetworkOptions]]
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+
+[[deps.OpenBLAS_jll]]
+deps = ["Artifacts", "CompilerSupportLibraries_jll", "Libdl"]
+uuid = "4536629a-c528-5b80-bd46-f80d51c5b363"
+
+[[deps.Parsers]]
+deps = ["Dates"]
+git-tree-sha1 = "621f4f3b4977325b9128d5fae7a8b4829a0c2222"
+uuid = "69de0a69-1ddd-5017-9359-2bf0b02dc9f0"
+version = "2.2.4"
+
+[[deps.Pkg]]
+deps = ["Artifacts", "Dates", "Downloads", "LibGit2", "Libdl", "Logging", "Markdown", "Printf", "REPL", "Random", "SHA", "Serialization", "TOML", "Tar", "UUIDs", "p7zip_jll"]
+uuid = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f"
+
+[[deps.PlutoUI]]
+deps = ["AbstractPlutoDingetjes", "Base64", "ColorTypes", "Dates", "Hyperscript", "HypertextLiteral", "IOCapture", "InteractiveUtils", "JSON", "Logging", "Markdown", "Random", "Reexport", "UUIDs"]
+git-tree-sha1 = "670e559e5c8e191ded66fa9ea89c97f10376bb4c"
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+[[deps.Printf]]
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+[[deps.REPL]]
+deps = ["InteractiveUtils", "Markdown", "Sockets", "Unicode"]
+uuid = "3fa0cd96-eef1-5676-8a61-b3b8758bbffb"
+
+[[deps.Random]]
+deps = ["SHA", "Serialization"]
+uuid = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
+
+[[deps.Reexport]]
+git-tree-sha1 = "45e428421666073eab6f2da5c9d310d99bb12f9b"
+uuid = "189a3867-3050-52da-a836-e630ba90ab69"
+version = "1.2.2"
+
+[[deps.SHA]]
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+
+[[deps.Serialization]]
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+
+[[deps.Sockets]]
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+
+[[deps.SparseArrays]]
+deps = ["LinearAlgebra", "Random"]
+uuid = "2f01184e-e22b-5df5-ae63-d93ebab69eaf"
+
+[[deps.Statistics]]
+deps = ["LinearAlgebra", "SparseArrays"]
+uuid = "10745b16-79ce-11e8-11f9-7d13ad32a3b2"
+
+[[deps.TOML]]
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+
+[[deps.Tar]]
+deps = ["ArgTools", "SHA"]
+uuid = "a4e569a6-e804-4fa4-b0f3-eef7a1d5b13e"
+
+[[deps.Test]]
+deps = ["InteractiveUtils", "Logging", "Random", "Serialization"]
+uuid = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
+
+[[deps.UUIDs]]
+deps = ["Random", "SHA"]
+uuid = "cf7118a7-6976-5b1a-9a39-7adc72f591a4"
+
+[[deps.Unicode]]
+uuid = "4ec0a83e-493e-50e2-b9ac-8f72acf5a8f5"
+
+[[deps.Zlib_jll]]
+deps = ["Libdl"]
+uuid = "83775a58-1f1d-513f-b197-d71354ab007a"
+
+[[deps.libblastrampoline_jll]]
+deps = ["Artifacts", "Libdl", "OpenBLAS_jll"]
+uuid = "8e850b90-86db-534c-a0d3-1478176c7d93"
+
+[[deps.nghttp2_jll]]
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+
+[[deps.p7zip_jll]]
+deps = ["Artifacts", "Libdl"]
+uuid = "3f19e933-33d8-53b3-aaab-bd5110c3b7a0"
+"""
+
+# ╔═╡ Cell order:
+# ╠═c7256818-f2ab-4f8a-be6f-1d2c97dca981
+# ╠═3e3e324d-5650-4f81-87cf-fb0f6f55d9d1
+# ╠═2ab6f97f-8eed-4b86-9eb6-1de88e6c846d
+# ╠═377a9100-efd8-479c-b9f6-68584c886800
+# ╠═0e62a7b2-0636-4018-b005-0ae674fec45e
+# ╠═6046417c-460b-4b0c-8423-4d6c4c18731f
+# ╠═3e21d34f-3758-427f-85c0-7c457f3f0904
+# ╠═4a07f5e3-2413-49c4-824c-b9c844695052
+# ╠═9008b1c4-ad76-4d4f-b6c5-001a77543b97
+# ╠═830dd737-4fdc-42c7-b105-d0622b055db1
+# ╠═f91b0c58-bc44-414a-b357-145d8c4339d2
+# ╠═3f1b8df9-104b-42c3-97ee-11782f9f744f
+# ╠═10c380fd-80e6-4cb7-b50e-1a7998ec00c5
+# ╠═58de483d-c2b5-4252-b6da-64bd8bfac1ac
+# ╠═4024358d-f673-45f1-a12a-00a5554622e3
+# ╠═b535fd1d-695d-49fb-8a6a-2f2f0053a6f6
+# ╠═63f32169-b98c-4212-bbd9-4c601266f209
+# ╠═cb49717b-0584-430e-a30c-c4d02cf55eb2
+# ╠═be428fea-fd34-4a08-94d2-c23ba0ecc586
+# ╠═da805692-8bf4-4eb5-a4ef-5a068c8a503b
+# ╠═268904d5-6252-4ff7-9d8b-315b73736cac
+# ╠═bc43e76c-3a9b-4f3f-9f88-28f2f7f868d1
+# ╠═0a2619e4-9eed-4eb3-a411-c616ee840062
+# ╠═bc8ef92b-1c68-4c9d-948a-6196dcd2b378
+# ╠═d8a2ae5c-b42a-4673-9a95-24cfc69ea3e7
+# ╟─c24c04e4-b131-11ec-2c1b-7de12fe0c324
+# ╠═279d81e7-77d5-4855-bf45-a1a613265f65
+# ╠═62e2481a-3fa1-4f2f-a7b6-7879c675701d
+# ╠═aa40dc25-6355-45be-b577-c5a8a28f1a8a
+# ╠═1ef034c9-da8d-4b35-8a98-532793b03718
+# ╠═e80c4d19-d746-4ab8-88e0-2389a722edb6
+# ╠═724f3fb4-1e49-4d58-a490-39d1110ba18c
+# ╠═431ffe1d-9e90-4344-ba35-0a5375954c0a
+# ╠═eb836cdc-de12-430c-a6f3-1524ebd28865
+# ╠═7e75da58-f110-41cb-ab19-79376370965f
+# ╠═6b417e5d-01c2-4b06-9708-62c422a6b64b
+# ╠═b621819d-6ce3-41e1-9e61-3ad0a2c9b016
+# ╠═0174178f-3ed9-4890-8482-714cb51a635d
+# ╠═d29338b3-3c25-4ae4-90d0-1176538c635e
+# ╠═2430f309-be28-4bc2-9692-92489c31f7b2
+# ╟─c7e76680-571e-427d-a564-8819df8b3750
+# ╟─00000000-0000-0000-0000-000000000001
+# ╟─00000000-0000-0000-0000-000000000002