Please help me after i flashed eu rom and i had all setup my phone was running fine after that i restarted my phone then lockscreen came again after then it started booting again and again (auto rebooting)

Whenever I try to replace my wallpaper, whether I do it from the gallery or the themes app, it tells me that if I replace my wallpaper I have to go back to the MiUI theme. How do I keep ...