Interrupts can happen when using a timer in encoder mode, but they're not particularly useful. What are you trying to achieve?
No, i never thought, that i have to start the "counter", since i was counting from the outside. Also did not start it as interrupt.
Its quite a bit confusing, that cubeMX integrates functions and code, but in other parts it doesnt, which is not so obvious, if you dont know this stuff well. I have to get used to it.