Reducing faces in Form?

[JetForMe]

I'm trying to model something that looks like a bowl with the center bottom melting and dripping. I started with a box form and have been pushing and pulling it. At one point, I wanted to subdivide a single face, but it seemed to subdivide all faces by 4. At the time I thought, well, I can work with that. But unfortunately now, it's too many faces to work with efficiently. I want to round out its shape as seen from the top-down, but it's tricky.  It would be easier if I could pick some edges to just get rid of, and have it approximate the new patch. Is there any way to do that? .f3d attached.

[TrippyLighting]

Observe tis in box view mode and compare with yours.

So model 80% in box view  mode and check in smooth view mode . Make minir adjustments in smooth view but then revert back to box view mode and refine were needed.