This is a common enough experience. Study the code you find here, keep learning, and compare how you feel about this in two more months.

I've been learning JS for two months and it took me more than 8 hours for find the right solution. I feel kind of stupid because my solution has 75 Lines and some other solutions I see here are very short.
Is this normal or am I really to bad for this?

Very good, but, why do you need three zeros in the array "bills"? It is also working with just two of them. Or not?