hope that this question was not asked 1000 times before.

I got a Distagon 50 4.0 C for a few bucks, but there is some fog and dust inside the lens.
As far as I can see - it is inside the rear lens part - the front lens part seems to be ok.

As I have allready opened/cleaned other simpler lenses without build in shutter - I am not
sure how to remove the rear lens element successfully. I have seen the two holes for
the appropriate wrench to unmount the back lens - but it seems to me, that this needs a lot of force
(which i would not apply at the moment). Is there something special I should consider ?

As mentioned before - I just want to remove the back lense group - not open/dissmantle anything else of that lens.

Many thanks in advance for any help !