don't mess with anything unless/until you are sure that you have a good copy of the correct wallet.dat stored in a safe place.
Very good advice.
3. meanwhile i realized an available update --> installed it
Version 0.7? That's the most recent release.
If it is "stuck" it could be because it isn't connecting to peers. Does the client show connections (status tray in bottom right)
The debug.log will show more of what the problem might be.