Thank you for replying so fast! I have cleaned out my game (removed the "infected" game, moved sims to library etc., this time I did not re-instsled the game) since last disaster that accured two days ago namely houses disapearing combained with frequent freez/crashes.
Nevertheless, I can see if I can re-cover the files through back-up.
I read another thread from 2014 where other gamers discribe the same problem http://forums.thesims.com/en_US/discussion/791146/save-size-suddenly-bloating-post-here. Fortunatly for some the problem got solved.
Still a very unhappy gamer and customer
FruUtter