How do I remove 4 pieces of tile in my shower?
You first cut the grout line surrounding the 4 tiles.  The cheapest tool for that task is a $10 grout saw like this https://www.lowes.com/pd/Marshalltown-2-in-Steel-Blade-Red-Plastic-Grout-Saw/1000204021.  You can remove easily 5 ft of grout line in 30 minutes with this tool and elbow grease.

Then use a drill make holes in your tiles.  Use a hammer and gently tap on the tiles.  Finally, cleanup the thinset left behind.