I m driving against the AI cars at the "pro" difficulty level. It seems that at this level the ai car are not very fast ...how can i increase their skills and the difficulty level?
THey are at max 'difficulty' level on pro. They do get better with practice, so make sure they have a full tank of fuel by filling up in your own setup and choose AI to use your setups in options. Then let them race. Over a series of laps and tracks their times improve, not a lot but they do get better. However in its current form LFS ai do not put up much of a fight against a human opponent.
But the AI aren't finished, so don't ever expect them to be very good in the current state. They also don't pit, have no idea about varying car parameters, and barely seem to notice you.
I'd recommend going online, but at the moment the quality of driving is worse there... Maybe in a few days when the 'OMG IZ TEH FST F! CAR' crowd realise they can't actually drive expect on playstations it'll be better, but for now choose your servers carefully. But it's good you want to practice offline first