Okay Egg here is the thing, there is 2 ways to turn around fast, G force and Speed.
The most G force you got you turn faster, and this depends of the jet you are using.
The speed depends if you are using Stealth or Attack jets, for stealths you got to keep your speed at 311-312 and maybe 313, and for the attack ones you got to keep it at 300-310 but as i said depends of the G forces the jet can handle.
Also you need to use your rudders, i mean your A n D keys, it will help you to turn around faster, that way you are not making a circle and you wont be moving in a straight line.
Theres a lot a videos that can help you with basics stuffs.