While you'll meet idiots who move to Berlin for 50k€, decent companies pay 70-80k€ for a mid-level developer. 90-100k€ isn't out of reach with 10+ years of experience, above that you probably need to switch to some kind of management.

Contract rates can be anywhere between 500€ (6+ months contract for a relatively inexperienced freelancer) to 1200€/day for specific and short-term gigs. Grossly speaking you need to charge twice your desired net salary in order to cover all the mandatory contributions, taxes and the risk factor.