I have solved the problem:
That's what I did:
Unlock the bootloader via htcdev.com.
Get the cwm recovery back
Flash the current cwm recovery via fastboot (my recovery was a little bit outdated).
Flash via sideload cm11 Rom.
Device booting until the bootanimation
Back to recovery do all the wipe stuff.
And yes i have fully working device now
But unfortunately I have not a RUU to get back to the factory defaults ....
But there are still a few RUU or nandroid backups that I can try ...
CM11 _ 4.4.4
Acer Iconia A501 16GB
Tegraowners KitKat 4.4.2 - V8