Do you think Mud enjoyed his life with the humans

Mud's life in a circus-themed shopping mall could certainly be a lot worse. Although, the fact that he's counted the days since he's arrived there—all 9,855 of them—should give us some indication that he's not completely happy. After all, you tend not to count the days you spend in a particular place unless you want to get away from it.
Mud—or Ivan as he's now called—barely remembers what life was like before he came to the mall. So living among humans is pretty much all he knows. At the same time he still retains enough of his identity as a gorilla to recognize that the mall is not the best place for him or the other animals. Instead, he figures they'd all be much better off in a proper zoo with ample space and lots of sunlight. Ivan has no understanding of life as a wild gorilla, so he's still thinking in terms of living his life in captivity. But some forms of captivity are better than others, and through the medium of art, he's able to communicate the need to improve living conditions for the animals at the mall.