I cant progress but good game!

This game is really fun but... Ive bought all the upgrades for the first car and everyone else is still faster than me Im on stage 3 and I have no idea how many stages until I can buy the second car. So if thats a problem the creators need to fix it if not someone has to tell me how I cans get faster (without in app purchases).

A car kid about EV3 - Multiplayer Drag Racing