These problem is concerning only the appearance of LibreOffice on Lubuntu.
I installed LO via the Software Centre of Lubuntu, but at the end there was a break (it was not finished). Later I tried to reinstall it via Synaptic Package Manager but it said:
E: Der dpkg-Prozess wurde unterbrochen; Sie müssen manuell »dpkg --configure -a« ausführen, um das Problem zu beheben.
E: _cache->open() failed, please report.
means dpkg-process was interrupted, do it manually to solve the problem. I did so and LO is working fine.
But now all the icons and menu labelling is very tiny in LO, too tiny. That's the Problem.
The window design is not from the Lubuntu desktop, (reminding me to win2k). So I guess it's not compatible with lxsession which I activated before the installation (in order to enable Hibernate, what is perfect working). I appreciate every Idea what I could do.