help my f4 5g is dying

I've had this thing, 8/256 poco f4 since 2022 july, nearly 3 years in and i swear its falling apart

battery feels so weak, even my other iphone 11 (just bought a new one this yr, used for work). usually a 85% charge from 10am - 3pm in ultra batt saver, no heavy games or social media, w 25-30% left.

not only that, it cooks so fast. 43* easily by playing warpath for 30 mins.

storage is mysteriously disappearing, like 20gb documents?? i dont even have any, yet it still takes up 20gb

overall peformance is quite slow, with 200/256gb on instagram, sometimes it lags while adjusting brightness

i still havent gotten hyperos eventho it was supposed to arrive in feb 2024

any advices?