Take a circle, make it a little bit bigger than the u-turn, take the circular track, duplicate it, and negate the duplicated part and union it with the circle. Take a square and union it with half of the circle to cut it. I will try to add pics of what I mean
Cylinders on roblox naturally are made out of different points and lines. You can see the sharp edges on the curve. You can just get bricks and follow the outline of the cylinder naturally
I agree with @TMG_ALT, Archimedes 2 is really great for this kind of think and it’s simple and easy to use, I really recommend it for your situation. good luck my dude.