This is what i think, maybe it's not right

1) Make a new account, i think you can't just press a button to restart
2) Look at the forum, there are a lot of topics that will help you out with good tactics
3) If you play on a mobile phone, there is a box where ''Stadium'' you can select. There you can choose out of a lot of options of what you can upgrade. Also, if you just play on the pc, under in the screen you can see a stadium. Click on it, then you can also upgrade your stadium

I hope I helped you a bit