When you arrive to the coner and stop, does that stop counts for the corner or do you have to stop again?
The first stop counts as 1 stop in the corner.
If lets say that one of the corners has the number 1 on it and you end your turn in the corner, does that count as a stop or do you have to do an additional stop?
It counts as a stop. Think of the numbers in the corner as "I have to end that number of turns in the corner" regardless of where you started the turn.
There are spaces in the straightaway after the S-turn shaded in grey. Why is that?
I'm not sure which track you're looking at on this one - all of mine look the same color.
when is it the right time to use the 6th gear
Use 6th gear when you're up to speed on a long straight I think I made it to6th once, then had to try not to overshoot a curve.
and how come when you shift up, you can only shift one at a time and when you shift down , you can shift twice?
Like racing with a real manual transmission, you would lose too much power if you tried to skip gears while upshifting (for example, 2nd gear straight to 4th gear). With downshifting though multiple gears, the transmission will help slow you down.