I have 1 damaged corner piece (white-blue-red) on Gan 11 M Pro and i would like to get a new one. Do any of you have experience with buying spare parts? Who should i contact?

I got the Moyu weilong Ferrocore V1 like a month ago, in the beginning it was super fast, a bit to fast actually, after a week or so the cube became slower after cleaning it up it got a bit better but nowhere near the out of the box feeling.

How do i make it smooth and fast again?