I decided to use the phpBB instead of wbb (aka burning board lite) 1.0.2
Well now I need a converter for this special problem.
As far as I understand and tried I am not able to use the converters from wBB 1.1.1 or 1.2 to phpBB and I was not able to find a converter for my scenario.
Does anybody know such a convertor? Or is semebody already working on such a converter and might need help?