Savegames are working perfect now, loads ingame, savestates and google drive sync working 100%.
Solved problems:
I was able to download savestates from google drive but they won't show up on my N7 after the update happend.
So i reinserted the bios-files to Android\data\com.dsemu.drastic\files\system...... and problem solved. This happens only if you reinstall drastic, if you just update via playstore the old biosfiles will stay in place and the savestates from drive will be okay.
As i didn't want to use the old bios files i saved ingame, then deleted these 3 files again. Savestats and ingamesave wont load now, so you'll have to open the ingamesave (*.dsv) in desmume (PC) and resave ingame. Copy file back to Android\data\com.dsemu.drastic\files\backup, delete the (now useless) old savestates in \savestates\ and fire up drastic. Load your rom, load ingame and then resave your savestates, upload to google drive works flawless.