CPU is the backbone of your computer so you need to check the resources for giving the good shape of your PC. So try to maintain the normal range of CPU between 45 degrees to 50 degrees C . And you are playing games than range could be between 70 - 80 degrees Celsius. For checking the computer temperature you can use trustable software. There are so many software available in market for monitor CPU temperature.
There is some technical issue in your battery so go for the external power supply option. Or press the Volume up button followed by the Volume down button and then quickly press and hold the Side button until you see the Apple logo to force restart your iPhone SE
First you need to clear the data from your c drive or you can move the data from c drive to d drive manually. Also you can use the third part software for clean junk file. I know it’s scary for your privacy to use any third party software but there are some genuine software which can fix this issue without harming your privacy or data. These are the best software for clean junk files and really boost your PC speed.