Okay I had a quick look, bearing in mind I'm not the best driver but I can see some points where I can give hints. Maybe some of this is obvious but I might as well say it
Starting: It looks like you could start a lot quicker - I don't think you're revving before the lights go out? I assume you have a clutch on your pricey pedals and this is the best place to put it to use - clutch down - -put it in first gear before the countdown and rev to
near the limit then slowly release the clutch and vary the throttle for maximum traction.
Hockenheim - Vette's are always quite tricky being heavy and slow turners, really a slow in / fast out kind of car. There are a few corners where you have a good braking point, but you stopped braking quite early, carried too much speed into the corner and went wide in the middle or on the exit.
For example at 77 seconds if you had have carried on braking a couple of metres longer you would probably have had a tighter line through the corner allowing you to run to the outside for the next corner, and avoiding the oversteer you got*. It was a good recovery though
Generally you could use a bit more space round here - at hockenheim - and most of the default tracks - the kerbs are pretty tame, so you can fearlessly get two wheels on the kerb in a lot of corners, moreso on the exit of corners than the entry as it is still quite difficult to turn in off of a kerb.
You could gain a lot of time in T1 by coming in to the corner much wider. I normally come down the S/F straight with the car as close to the kerb as possible without touching it, turn in to the corner about half way down the kerb (varies by car) and aim for the posts on the inside of the corner. As long as you're not going very slowly you'll always drift slightly wider than that, and normally end up just running slightly over the inside kerb. then if it goes right drifting to the outside kerb on the exit. It's not an easy corner to get perfect though.
Imola - Your line round this track was pretty decent and it showed with the P1
. Just a case of practicing to see where you can push it further, again a couple of times when you could have used more of the track, but good overall.
It's funny watching the offline races as I've never tried the AI in GTL - At the start of Imola you can just charge past all the AI cars on the inside because they mostly follow pretty slowly in a neat line. You could never do that in an online race. It also doesn't help so much with getting in good laps when you have to go to the inside to overtake everyone
*short shifting would also be useful here - changing to a higher gear slightly earlier than usual would have stopped the rear wheels from spinning and prevented the oversteer.