Why do evolutionists believe that humans are fish, I don't have any gills and I don't look like a fish

There is something very fishy about that theory!

I heard someone say humans evolve from frogs on here.

Well, no, but human embryos and fish embryos look very identical in early development. This is common in many vertebrates.

Humans are not fish, and that's not what evolutionists think.

We had a kid in school who had gill slits when he was born. They had to be surgically closed.

because life did not evolve on land

Oh dear, sounds like someone flunked the 3rd grade. Again.