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