What does mais je ne sais pas sur de ce qui est engras mean in Spanish?

"Mais je ne sais pas sur de ce qui est engras" is French, not Spanish. It means "But I don't know what is fat."

Here's how you would translate it to Spanish:

"Pero no sé qué es gordo."

This translation retains the meaning of the original French sentence.

Let me know if you have any other French sentences you would like translated!