Photoshop 21.2 Layers issue

Ive been having trouble with a few of the latest versions of photoshop. It all has to do with the visibility of the changes made on a photograph not visible. In the lastest photoshop version if I drag a new layer onto another one. Where ever the image lands imprints itself in that position. I can move the layer but when erasing it reveals where the original layer had landed in the past.

Im not sure if every new version of PS requires faster computers but my imac should be able to handle any new software.

Any help welcome

Tim