So, do the Perks like Power-Bash in the Block-Section of the Perksystem work with a bows Bash? For example, can you disarm and opponent, or deal five times the damage with the bash?

yes.

"yes"? Interessting. Can someone confirm this, maybe? No offense intended, Rukioish
And, btw, is there any realistich way in increasing the blocking-skill as pure Archer without relying on Trainers? Power-bashing with the Bow doesnt′seem to increase the blockingskill.

Since the only commands with the bow are bash or shoot an arrow, you'd have to switch to a shield to gain any levels in blocking.

I thought that much, [censored]. Thx, anyways. No I have to consider if the power-bashs worth it.
Where′s the Master-Trainer for blocking?