Why does he have to win I didn't understand

If he wins, then he’ll get a chalice and a reward of his choosing. He wants to use that reward to go home!

I think, he doesn't want to be a shahbanu nor become the padishah's wife.

Yeah! That’s exactly why he doesn’t want to win, so he can go home

That would be difficult. Shuraka's gonna release hell if he leave. Plus, he's gonna burn all of chase's letters.