Using the [Search] box at the top of the 'CZ82 & CZ83 Club' forum page, type in
mag release and click on the [Search] button to its right. Some good ideas for working on, what to me, is the weakest link of the CZ82/83 pistol design will return to give you more info on this relatively common problem.
Sailor Curt's "Captain of a Crew of One" website mentioned by Psyop96 is one of the best sources on CZ82/83 dis-assembly that I have come across. Massaging the mating edges of the magazine catch components helped on a couple, but I had more success with replacement parts purchased from CZ-USA
http://shop.cz-usa.com/czpartslists/CZ83.pdf. Good luck!