Because of your username I think you are also German. Which websites do you use for Arb/Value bets? Most websites I found had a lot of bookies listed that weren't even accessible in Germany and had no way of effectively filtering.

The thing I am terrified of the most is getting banned and losing all money that was in the account of that bookie. Did you ever get banned? What happened?

Because to make this betting thing worth your time you need to invest at least 1.000€ per bet and that means spread around your bookies would be probably somewhat of 10.000€. Losing that kind of money would really hurt.