iPhone 15 Pro very laggy and “non genuine battery” message

Ive been using an iPhone 15 Pro for the past 2 months without any issue, then 2 nights ago it started getting really laggy when i try to use it and kicks me out of apps for no reason. It started getting worse when i got a non genuine battery message out of nowhere and it would overheat like mad, i dont know if this is my fault or is the battery already dead. any fix would be helpful