how do you guys learn unity 6.5 and all the code c#

Learn by doing, and by study.

For the C++ stuff, we used to have a book list that very closely mirrored those used in various discussion groups. This one continues to be updated and is still valid. Most of the books in the current list are the same books just the 2nd, 3rd, or 4th edition as the language has updated.

For C#, the type of programming done in Unity very often is only minimally structured and most beginners treat it as a scripting language rather than using it as an in-depth programming structure. It's more about finding the library functions and using them effectively than it is about the C# language structure.

You write that you're in college, those assignments are important. Don't just mindlessness do the assignment, and definitely don't just use chatbots to write the code for you. Use them as a way to play and experiment, ask yourself "what happens if ..." and see how systems work one variation at a time.