Add on, Ads by Great Find, I have the option to remove and do this but it remains and these adds display all over my web pages Especially Sky Sport.

I discovered recently when I log on to sky Sport My webpage gets cluttered with ads "Ali Express" There is a name Adds by Great Find. I found it in My add on's and am given the option to disable or remove. I choose remove and it is removed. sadly the next time I log on it's back. Even when it is removed the adds still appear. I sent a screenshot to sky sports and they advised I check with Firefox I need to rid myself of this as it is an insult to have to keep seeing this nonsense. I hope you are able to help. Thanks Alwyn.