Turn on a popup blocker in your browser, it's built-in under settings in most browsers. You can also raise the security level in your browser, which should block some of the adds.
I would check your computer for malware. Download and run Malwarebytes (free malware removal tool) from https://www.malwarebytes.org/ Once the scan runs remove all the threats it picks up.
restart your machine and run it again to make sure everything is removed.