I've heard on this board and several others about controllers being blown due to overheating the motor and topics like that? What does this mean? Do I have to avoid hills, avoid overuse of the throttle or anything else?
You need to make sure you are in a low enough gear to be able to pedal easily just as you would without a motor.
Using full throttle from a standstill especially in a high gear will cause overheating.
The earlier BBS02s had issues due to weak fets but newer ones are a lot better.