S. T, i'm another one who looks for your answers. Hurry back. I already miss you.
My cousin, who died a couple of years ago was an IT tech. When I had problems such as you and others describe, he would run a program that cleaned out the computer. Helped every time. He's gone and so is whatever program that was.
My son-in-law installed a security app called CM Security when I was having difficulties. It cleans out everything as I use my phone. My cousin said cookies were bad. He set the computer to not accept cookies. IT Security cleans them out when I leave the site. Cleans out personal browsing every couple of hours. Warns me when I'm about to go to an unsecured site. It tells me that the phone is using.too much power and optomizes speed. It does other things that I don't remember.
CM Security works better than the other one. Can't remember it's name. It's very popular. It only checked for viruses. CM Security is free, is regularly updated, and has a very good reputation.
I either use CM Security's browser or Chrome. I don't use Adblocker. Ads don't bother me.
The only problem I have from time to time occurs late at night. When I type, the letters are slow to appear and the page is jerky. This tells me it's time for bed.