Suggested

pit STOP

I'm afraid you can't, the stopping times are random. 

That part of the game was removed for this new mobile friendly version of the game. I don't know if there are plans for it to have a comeback but since this is suggestion: I'd like if it would, and fuel amount had an impact. 

Yes, hire and train pit crews, technicians and so would be really nice to flesh out the managing part of the game.

Everyone has sometimes better and less good stops and all average out at 4.5 seconds. But there is another thing, cars can block each other in the pit lane and depending where in the pit lane your pits are located it's more or less likely to be affected by it. More about it in Joey's advanced guide, mainly in part 3 and the end of part 4.