Finally, I decided to order a new optical drive for 49$ to make the update of the firmware from my MBP…
The firmware update was easy, i just followed the instructions given on that forum…and my MBP works flawlessly now! No freezing anymore!!! 
However be aware if you change your optical drive that you could experience a problem with the wireless afterwards…
Indeed, after 30 minutes of normal internet use, my wireless went off, and i recieved the message “No hardware installed”…
I solved the problem by unplugging and replugging the cable of the Camera/Wirless that goes on the top of the optical drive. It can be a bit tricky to reconnect to the motherboard (you can not really make sure that it’s plugged in correctly)…
