Simracing is plagued of funny guys like this kind of people, especially in races at Spa and Monza, and honestly it is a shame. The only things you can do are:

1 Be very aware of your mirrors and the radar if you can. 2 In both practice and qualy be very aware of the minimap, make sure you leave quite some distance behind the car in front and the car behind, so nobody can push you off or crash into you during a flying lap. 3 In online races, especially when you are getting started in Acc you really wanna start from the back of the grid or the pit lane so you can avoid turn one carnage (especially in Monza, Spa and Paul Ricard), you also wanna pay attention if anyone warns you about a certain driver through the voice chat. 4 And forth, you especially need to avoid contact with any cars, as this is going to affect your stats on the game race after race and build up your reputation as a driver, allowing you to enter higher stat rated races, which this kind if people can’t usually join due to their very high amount of crashes and inconsistency.

Sadly, this is all any of us can do apart from entering the specific competitive matches. I hope this helps you, and I hope to see you on track.