So my tutor and I have been talking about this example and I still can't ascertain an answer I understand from him as to why it works (the piece in bold).
ただ走るのではなくて サーかを しながら走るのがいいです
What I understand is that the の acts as a noun connecting piece, just as こと would. What I don't understand is how he has connected 走る with ではなくて. Is this the latter a noun? I really don't understand its use here. Why not say 走っていないけど？