Solved

One question about the cars

In the section Home i can read level of preparation good (livello di preparazione buono in italian) and clicking on good it's written pilots ready, cars in conditions to run, cars updated (every in green), but i've not changed parts and engines. Now, what's up if i don't change the parts and engines for the next race? My cars will be slower even if the game says that it's all ok  (all green) or i'll be competitive?

If you haven't changed engines and haven't repaired car with parts then yes your car will be slower compared to other teams who did repair engines and repaired cars using parts obviously depending on car design and strategies etc. In short used engine will be slower than new engine.

Thanks