Normal rule of thumb:
If you are ahead, you own the corner, if you are side by side keep your line, meaning inside or outside line. THATS not racing line!
The racing line is the normal line you would drive in a hotlap, so the guy was wrong.
If you are lapped let the faster guy do the work, he has to take actions and also has to take care of things. He also has to take the responsiblity if theres a crash.
Use good "body" language, what i mean is start to take an line and stick with it early, the better you do that the less there will be tangles.
Dont move over in the last possible moment, do that when the other guy is still a good margin away.
If you want to let someone past while beeing lapped the easyest way is when you take the outside line, let the guy pass inside and wait and turn in after him and maybe catch his slipstream.
If you drive an oval is generally a good idea to take either the inside line and keep low, or the outside line and stay away from the inside line. The normal racing line is only possible when your not side by side.
Dont weave on straights, thats generally not good racing, you can do one move in race situations, that means one change of lines, if you are ahead.
Dont worry, just appologise if a crash happens and have fun in the next race. Even when you race alot in ovals and know the people around you mistakes happen, especially with the fast cars.