Start slowly
Joke apart, you should try offline for a while, doing slow laps until you know your way around the track.
Then increase your speed and try to find the correct lines through the corners. Press "4" in single player game to get a display of the racing line (not the ideal one, but quite good).
Then you are ready to go online and race others, or continue offline with the AIs.
AI's ignore you most of the time, so you will be wrecked.
Some demo servers are about the same as AIs, so do not insist if you meet that - change.
Don't forget to do the training - while not a "racing" training course it can teach you some car handling.
Get setups online (from others or websites) to improve your times, browse the forums for them if you seek setup building knowledge.
You will improve your racing when competing with others more than by yourself. Online play in the main strength of LFS
Welcome and good luck!