How to import a file in python?

I checked the other answers and they work somewhat but also give a ton of errors. I and My friend are working on a project in which we decided it would be easier to make files instead of having all our code on main.py. However, this has left us with a ton of bugs. Import [File name] works however it presents an error every time we run it. The code also says that the file is imported but unused which has left us confused.