I have some simple question.
Is it possible to make a great game with Panda3d ??
Is this library an interface between c++ and Python?
If so, will the quality of the product not decrease in a big game ??
and if panda3d have a good future??
I believe very much so, yes.
It has such an interface, but that’s not all that it is; rather–as I understand it, and broadly speaking–Panda is a C++ game engine that can be operated via Python bindings (along with some Python-specific classes).
There are some caveats to working with Python, but for the most part… not really, no. I’ve found that one can make quite large and complex projects with Panda, I do believe!
Of that I have no idea!
i have a question if you are willing to answer it?
Speaking for myself, I don’t know whether I’m willing to answer until I see the question!
However, do ask! 
(That said, unless your question continues from the questions given by the original poster, it might be preferable to start a new thread for your questions. That way people searching in the future for answers to the same or similar questions are more likely to find them, I think.)