Nice pictures and corals. You are doing very well for being new to this. What lens are you using?
Depth of field was the hardest part for me and I still get it wrong often. Just remember increasing f stop to increase depth of field lowers the aperture. That means you will lose light and probably need to compensate by increasing the iso and/or using a slower shutter speed. I use a Nikon D7500, but the sweet spot for me with my macro lens shooting top down is f10, iso of 64o and shutter speed of 1/320.