Interesting story so far. It could do with flowing a bit more organically. Like why did they turn the MC back into a stallion already if they were fine with being a mare and why was there already a big time hop when they hadn’t figured out living arrangements and a bunch of other world building things.

When did cosmic become male again I like when he was female

Jumped too much, there's no buildup for this chapter, almost to no explanation, and, as Aiwhisper said, the main character was fine with his/her arrangement. That's not to say that Faust herself said that there was no turning him to his original gender, and now there is?