You don't necessarily have to alter the gear ratios. You just have to be able to handle the car. It's the only race in which you really have to drive it fast, if you can't do that, practise.
Some setup changes... take off the ridiculous toe at the rear wheels, turn off all driving aids (maybe TCS can be left at 1) and max the downforce. That should be a good starting point. Then drive practice laps one after another, tuning one thing at a time to see how it affects the handling. When the car is as good as you can get it, you're ready to race. If you still can't keep up, you're just too slow. Sorry to be blunt but that's how it is. In that case, keep practising. 👍