........WHICH ONE IS RIGHT ?!! .........
Which one is right ?
Do you mind stopping playing piano ?
Do you mind to stop playing piano ?
Do you mind stop playing piano ?
I think the first one ! am I right ?!
which one is your choice & why ?
"Will you stop playing the piano?"
or if you're me:
"Stop playing the piano."
Do you mind NOT playing the piano?
The first one actually is correct, it sounds clumsy, yes, but a lot of natives would say that.
E.M,
Congrats, for you may have some intuition developing. Though the wording is clumsy, the first one would not give away the person as a foreigner or one who speaks ungrammatically.
EM, the first is a bit clumsy but could be said, apart from the fact (which is not the focus of your query) that you have left the definite article out. That would give you away as a foreigner. Playing THE piano. I don't know why we say "the". He was playing the guitar. He was playing the recorder. She was playing the flute. It doesn't really mean a particular piano or flute, it feels more general in these circumstances, but the definite article is reqd.
Stop playing that fucking piano.
Or... if you want to remain with your original structure, you could just say, "Do you mind??" The person will know you're talking about the piano.