Has anyone ever seen something like this? I don’t even know what I should do with the puzzle...
Any suggestion or help is welcome!
I haven't seen this particular puzzle before, but this seems to work:
Take the loop marked in pink. Push it through one of the holes, and around the knobbly bit's end. (The one that's closer to the string's end coming through the same hole we just went through.) It should now look like the string drawn in yellow.
Then, bring the loop around the other knobbly end, but pass it through the fixed loop of the other end of the string first. This is depicted by the green string; you should end up with something that looks like the light blue string.
Then, pull the loop back to its starting position back through the hole, and there should be only one string going through the pink loop now.
Repeat for the other hole, and the ring should come free.
(Edit note: my earlier answer went through an extra loop, which turned the whole method into a complicated no-op. This new one should work better.)
The goal is almost certainly to detach the ring (and then to put it back) by careful manipulation of the bits of the puzzle. I haven't seen this exact one before (but I'm not an expert in such puzzles so that doesn't mean much). Solving them often requires you to do things like forming part of the string into a loop and passing it through a hole / around a piece of wood / through another loop, etc. Sometimes it helps to imagine that all the components of the puzzle are more flexible than they really are, so as to make the solution easy, and then try to "deform" the solution you get into something that works for the actual puzzle.
In this case, one thing I'd try is seeing whether that loop in the middle on the right can be got to one of the ends of the string, passed through the loop at that end and over the cube, and brought back again in some helpful way. (But, again, I'm not an expert on these puzzles and that may either be impossible or just make things worse.)
You might want to take frequent pictures as you do whatever you do, to make it more likely that once it's done you can undo it.
The google results for this shows that it is a "Disentanglement puzzle"
These are a type of mechanical puzzle that involves disentangling one piece or set of pieces from another piece or set of pieces.
For the mentioned puzzle, the goal is to separate the ring from the puzzle strings by making loops out of the string and passing it through a hole or some wooden or string part of the puzzle.