IPhone 7 FPS problem (Call of Duty: Mobile)

Good day, everyone.
I faced such a problem that after installing the Mobile code on the iPhone 7, it immediately starts Game settings at high, and so she played at high Max fps without any problems.
I decided to enter the royal battle and noticed a loss of frames, unlike team fights, well, I decided to lower the Settings, but the game did not work better, well, I thought it was poorly optimized, I stomped a little bit and went back into a team battle, and then I noticed that I was sagging fps on medium settings, also small friezes
I reduced the graphics to a minimum and turned off everything except high fps, but the game also sags and freezes, I played a little bit and left, went to the pubg to skate, after a couple of days I went into the code that also worked , and then decided to return the Settings to high, started the match and the game crashed
After the restart, the game began to work clearly at 60fps at high settings, in short I played and again went to KB, and again I lowered the Graphics Settings in KB, and again my game works poorly everywhere I
set any graphics parameters and it works stably with weak FPS and mini friezes on any graphics settings are the same, only the picture changes slightly slightly.
In addition to this, it also eats a battery, the phone is like a Skovoroda.
Can you please tell me who had this problem and how to deal with it?