There is a sample.htaccess file that ships with b2evolution. You should try to use it.

http://b2evolution.net/man/htaccess-file

I did already without results

Can you please help ``??? I restored everything so far but B2Evolution does not find its contents!

I am desperate and stopped the adwords and facebook already!

Can you please help ``???

That is why I hate updates so much, they recommend you to update and then you are with a broken updated version that brings some how a new problem!

obviously there is an incompatibility with mode rewrite

in my apache config I can set up diferent versions of PHP

5.2 as apache module
5.2 as cgi / FPM
5.3 as cgi / FPM
5.4 as cgi / FPM
5.5 as cgi / FPM
5.6 as cgi / FPM

wich one should I use ?

http://vertrauliche-entsorgung.colonia-aktenvernichtung.de/

I'm just quickly answering your comments, I'm in a hurry right now and can't go into details.

Having a backup of your site is a golden rule. Do you have any (if you followed the auto-update process, a backup file was automatically created)? Can you restore that backup to get your site on-line again while you figure out why the update doesn't work?

Can you test the update of your site in a local environment? The more complex your site is, the more careful you need to be before performing updates or any other complex process.

I have a backup and I restored the .htaccess but it doesn't work

I try to figure out if the SEO and URL Settings are different or if the new B2evo requires a diferent php version

sorry I made obviously stupid mistake and forgot the "."
so my .htaccess didn't work as it was erroneously named htaccess without dot!

Is the problem already solved?

yes this one is solved -- only my update problem with another B2 blog still exists!