Is there a function key lock or something like that on a Mac?

Settings -> Keyboard -> "Use all F1, F2 etc keys as standard function keys"

You may like FunctionFlip. Here is a description from it's website:

FunctionFlip's purpose is simply to disable the special features — rewind, play, mute, etc. — on the function keys. For example, if you "flip" F7, F8, and F9, those keys — only those keys — will revert back to normal F keys. Press the fn key with the special key to get the special function back. That is, the "special" and "normal" functions are flipped.