Acer Niro 5 AN51-51 - My cpu clock speed is very low when in gaming 1100-1300Mhz

mhasandx

I have brought this Acer Niro 5 AN51-51 in 2018. For now i mostly play Apex legend games. When i start the game , in the main menu my CPU usage is like 30-40%. but when i start a match, the CPU uses JUMPS into 100% usage mode. For first 10-15 sec my CPU clock speed remains above  2.5Ghz . After sometime the clock speed decrees and stays @ 1.1Ghz . Also the CPU Temp is 96°C. and GPU Temp is 90°C . this causes the game to stutter. and the FPS decreases to 25-30FPS.  Thus the game being unplayable
So . i am asking for help how can i solve this type of problem
I will attach the screenshot of msi Afterbuner later

mhasandx

Here is the screenshot of MSI AFTERBURNER 
IN game menu


this is when i play a match