[Mashiro]

You want to modify code inside executables? This is not entirely possible. Executables are machine code and not any of the programming languages the humanity knows. Compilers translate the programming languages we know into machine code and provide these as executable files.

I said "not entirely" because there are certain things that can be edited through Hexediting programs and Reverse Engineering like text parts or hex codes. Reverse Engineering is however a really hard thing and requires far more than just programming language knowledge. You need a lot of experience to reverse engineer the source code of a application from its files.

There are however programming languages like Python or Java that are compiled at runtime. So you can still see the source code in the respective .py and .java files. These files are sources for the runtime compilation process. Programs written in these languages aren't stored as .exe executables.