Greywolf1: I never had this problem. So you answered the final riddle ("What force and strength ...") correctly and received the piece, but it doesn't show in your inventory, nor were there any messages.
I haven't been in this dungeon for some time, so I don't remember HOW you received the piece. Did you have to pick it up? Was the fanfare for solving the riddle or for obtaining the piece?
Perhaps you could watch one or two playthrough videos?
MychaPL: I solved the riddle and I litterly can pick up the pice but game can't fully register it and thus I can't get the window with infromation what to do next. I pick it up, it dosen't apperes in my inventory and the pice respawns every time when location is loading.
The piece respawning sounds like a major glitch that has been used to speedrun the game. If you see the item you need to retrieve from a story dungeon respawn, *don't* pick it up more than once or you can cause the game to think you have more pieces than you should, which can cause strange results.
If you've already picked up the piece more than once and saved, you unfortunately might not be able to continue playing normally on that save. (I don't know if there's a way to skip just part of the game and play the later dungeons normally; would be nice if there were.)
