first you need a pc and than use third part software program good luck

you should do as the repairman say if you leave your screen like this the issue will get worse with time

i can see you have software issues, you can check your last update or see if you didn't updated you phone yet if the issue still show you can do factory restore your device . good luck

i can see your problem be the CPU if you look close your processor is Intel Core i7-8550U 1.8 GHz and the U means "ultra-low-power," they're instead low-power designs made with efficiency in mind. They have lower clock speeds, lesser cores, and more importantly, a very low TDP. all the other part of your pc is good but you can search for way or solution for your processor to be faster good luck