Ali,
Sounds as though you have a common problem that almost all older SLR's have, deteriating light seal foam. I would suggest you go to the Classic Camera Repair Forum and do a search of your camera. I'v seen a number of sites on repairing Praktika cameras and lens. In the unlikely event that you cannot find your problem resolution, you can submit this question to the forum. There are a number of members that have worked on Parktikas and someone will respond.
There is a world of information on your camera make on the web. Just do some research and you'll find detailed free repair manuals, as well as, important hints/notes on how to proceed. Replacing light seals is a simple but necessary task. If you don't replace them you will have light leaks on your film.
Good luck.
Charles Harbin
July 2007