iPhone 7 Plus restarts after 3 minutes on 1 % percent battery issues

Please I need your help .. My iPhone 7 Plus screen fell and had a hair like crack but it did not give the phone any problem .. after one month

My Iphone started acting up , it restarts after every 3 minutes when I’m using it and comes on at 1 % when it was charged fully well ,

sometimes the battery percentage goes up and drains down and when it reaches 20 percent most times it stops doing the random restart ,

also when I am charging it it might stop charging and sometimes charge when I replug the charger ..

I have tried my best by doing a reset on my phone and I’ve updated the software to the latest IOS (12.3.1) and also deleted apps and erased all settings , but I’ve not changed the battery .

I don’t know if it’s a battery problem or it’s a software problem or something else

please what is the solution to my predicament??