Q: Itunes doesn't update correctly

Dear Community ,

I have Mac OS X 10.6.8 and need to update Itunes to Version 11.7 (at least), because I want to synchronize my new IPhone 5S with the old back up data of my Iphone 4.

But (and that's where the fun starts) Itunes didn't update correctly to the 12.Don't-know-which-number Version as it was planned to, so it is stuck at the 11.4 Version and I can't even update to any higher Version, because it says that I already installed a higher Version (yeah, sure, buddy -.- ).

Please, please, please help me!

Thank you!