Basic question about Merging faces I'm a beginner with blender so this is probably a very basic question.

I have this basic model below. I've ended up with a lot of unwanted geometry that I want to simplify.
I wanted to start by merging the two selected faces below but no matter what I try to delete or merge it just destroys the geometry.

How can I achieve what I want to do (which is combining all of the unwanted geometry, either starting with this merge or some other way?)
Select the faces you want to merge, press Del or X and click limited dissolve.