Thanks for the info, I really always thought that after 21 mio bitcoins no more blocks could be mined.
That brings me to another question:
Has anybody an idea of how high the fees are that are earned for mining one block in average?
It varies. Bitcoin blocks have a limit of 1MB and the transaction fee recommendation goes around the 0.0005~0.0009 per KB range. 1 MB is roughly 1000KB and majority of the blocks are full so it's 0.5~0.9 per block (0.7 average I guess?).
There's also
this chart which shows total transaction fees each day. The number of blocks generated each day is 144 average.