Hello again...
This here is a website for the simulation "RFactor".
You are driving the simulation "GTR2". For this game our brothers of
www.pilsbierbude.de are the specialist. They also have a forum, maybe your questions will get better answers there.
But, to your question: If you want to play online on our servers, you always need a complete installation of all cars ,tracks and mods the updater has downloaded. Deleting any by hand will cause troubles, such as you won´t be able to join the servers.