Hello @Luca_Airoldi welcome to Zwift forums.
In the bike industry - it is standard that the right pedal is normal threaded and the left pedal is reverse threaded. The left crank is reverse-threaded to match. The arrow on that image shows the correct direction to tighten the pedal.
Please also check the pedals themselves. They should also be clearly marked left and right.
Your photo and description seem to show the left crank, and if so - that is installed on the frame correctly. As the threads are now damaged - please contact Zwift Support to discussion options.