pycharm
Pycharm has an excellent debugger, so it is worth investing some time in this IDE. However it is horrible to find some options that seem trivial to regular users.
Click the python interpreter selector.
The f*&^@ is the python interpreter selector ??? You should have used pycharm for a year to understand the documentation !!.
If you search on you will find that it is in the status bar : WHERE THE FUCK IS THE STATUSBAR !!??
Enough with the frustration, I will list here all regular actions needed and common errors.
status bar and python interpreter selector
It is the lowest bar on the screen with left a message, and right encoding, interpreter, git branch etc :

The interpreter part saying python 3.9 is also the selector when you click on it. Sometimes 'add interpreter' just does nothing or maybe has a modal dialog somewhere unfindable so stop and start the IDE and it will work again.
interpreter
The easiest way is to use the system interpreter, but if you use virtual environment please note the it will be installed under your project and so if you delete a project you will be left with a non-existing interpreter.
git diff
My most used command is not there in the git menu, i have not found a solution for this yet (command line)
run configuration
You always have to create a new one after checkout, but it follows itself. When you try to run it wants a run configuration and offers you to choose one.