How can I rid my world of Grammerly.

I signed up for Grammerly but used it about two times and immediately asked them how to disable it. I followed instructions, but it keeps coming back. I don't remember my password, and they do not seem to think it is still on my computer. Every time I try to fill in anything online, it "checks" and as a former English teacher and published writer, that is insulting, irritating, and drives me crazy. If this doesn't stop interfering with everything I do on Firefox, I will go back to Chrome or something. Please help. It is invasive, irritating, and totally unnecessary. It checked this message and highlighted their own name as a critical issue to correct. thanks,