How do I find the source code of a .EXE!

Can anyone help lead me down the right path here? I need to gain knowledge on how to decompile and find the source codes of executable files. I want to learn this because I want to see how a program I have is made. Just started getting into this and I am curious to see what something simple like the program I have looks like.

what kind of source you will get honestly depends on the program as programs built in c#/.net that are unobfuscated you can easily decompile with dnspy and get their full source whilst other ones like c/c++ programs unless you have debug databases you will have try figure out what it does based off the assembly or if using a decompiler such as ida or ghidra you might be able to get pseudocode of functions but no variables or function defined within the source itself will be viewable