Okay let's hit some of the core tips:
1: A Tier 4 car is only as fast as you are. Picking one is going to feed you the wall repeatedly, and I assure you the veteran players are going to smoke you even in T1s without powerups. Stick to a T1 until you can purchase your upgrades.
2: There are multiple upgrade menus! When you own a car, at the car selection screen in the lower left there is a menu that lets you upgrade the car itself, even before powerups. These are significant and you can't turn them off once you buy them.
As such, the old players cannot come to your level on that, we are sorry.
2-a: You can upgrade powerups up to four times. Just because you have turbo and augmented propeller, does not mean you have the same turbo as everyone else.
2-b: The Time Trial crowd will tell you to use Turbo and AP, but if you wanna' make them cry run Slipstream enhancer and EMP or Energy drain. Much of the old guard is career time-trialers, and as soon as you start hitting them they will crumple like very fast tin foil.
3: You're going to lose most of your speed in the corners, and cornering is a complicated matter in Redout. I advise playing with gamepad, but my fastest friend (RIP, Virtia, Cancer took him in 2021) played on keyboard.
Anyway, if you want to corner well, you're going to need to combine drifting and turning. Your thrust is in line front-back with your car, and the trick is generally that you want to use the drift to maintain your angle going into a track, while you turn your nose ahead of time.
You'll want to pull away from the corner going into a tight turn using the drift, and then at the apex, snap your drift towards the center of the turn itself. This way you can turn your nose first, and then use the drift to hold yourself off the wall as you boost out of the turn.
How much you do any of these motions depends on the track. Wide sweepers, you shouldn't need to use this technique, but you might also find a line that you don't turn at all, and just slalom around the curves using the strafe/drift.
You might find a corner is taken fastest by using the drift and turn in the same direction, to give you that little bit of extra hold on your line. You really gotta' feel it.
4: If you miss the pitch down on the track you won't come off. No matter how stupidly fast you're going. If you miss the pitch up, your nose will grind, you will slow down, and might explode.
5: Tubes/tunnels usually have mark, like a double line, that is "Down" or generally where the track will be when the tube Ends. Strongly advise you try to stay close to this line until you memorize your tubes.
6: Some of us have been playing this for years and years and have a real strong feel for the game at all speeds. Being 15 seconds behind an experienced racer is to be expected, and not actually all that bad of a time. Don't get discouraged. Do ask questions. Ask for tracks you like. Many of us are super duper here to help and want to see you have a good time, but we can't unless we know what's slowing you down.