Also, have you tried AdBlock? https://getadblock.com I use Opera browser and AdBlock together, works great for me. I NEVER get unwanted pop-ups, plus I can right-click on anything on a web page and block it if I wish.
Also, if your computer has a lot of annoying junk popping up, there's no telling what's been installed and a clean fresh install of Windows should be done. Then find a browser of your choice and install the AdBlock above. Sometimes it's best to just do a fresh install to get rid of all the potentially dangerous junk you may have unknowingly installed.
I used a free VPN before, and it was pretty okay, but I had problems like slow internet, and it would cut out a lot. Plus, the constant ads were annoying.
That's why I switched to individual proxies from proxys.io. It's way better for me now. No more ads popping up all the time, and my internet doesn't slow down or drop out. Plus, it's cheap – I only pay $1.4, which is suitable for not having those ad hassles and better internet.