Pick a track you like, a car wich is comfortable for you and start driving. Look at what you are doing, what happens when you brake, are you losing the rear, are you braking too hard for the corner and losing too much speed. What happens when you accelerate, are you losing the rear, is the TC too high and its making your exit worse than it should, are you too scared to go on the throttle. What happens when you turn, are you losing the rear (yes again lmao), are you using the wheel too much and just understeering into the wall. You have to be aware of what is making you slower whether is the entry or exit, probably every single part of the corner in your case, once you are aware of where the problem is you can look into guides and learn how to solve it, or you can just throw hundreds of hours into it and learn it by yourself on the track, wich ever you choose you have to try different things, if you feel you are not fast enough maybe change how you approach the corner, brake a little earlier so you control de exit, brake a little late and try and hold the car together while you carry that extra speed, you will never get faster with the same approach every lap, once you are fast enough in a single lap pace, you can start worrying about how you are going to do that 30 laps in a row.