network issues

I purchased the phone on 5 October 2019 Samsung Galaxy M10 After using couple of months phone becomes slow or the performance of phone degrades there is no network issue in phone when I buy it but now some issues are appearing like phone automatically restarting Phone automatically restarting is resolved after hard reset Other issue is network issues Phone holds the good network in indoor coverage but now it Is not holding good network in indoor coverage You are saying that there is network operator issue but how another phone that's Samsung Galaxy M31 hold good network in Indoor coverage I use both phones on same room M10 is having network issues but M31 doesn't have network issues Both phones are from Samsung How this comparison in network in both phones