Replicating a PWM in output

Hello, I'm new and I'm a university student. I'm doing a project with Arduino Uno. I should be able to get in Arduino with a PWM signal and go out with the same PWM. I have tried in various ways but I think the best idea is to use interrupts: RISING and FALLING. Unfortunately I do not understand what does not work, especially if you can enable the two modes for the same PIN interrupt (2 or 3). I would be happy if you could help me and advise me some solution! Good evening!