Remove shower enclosure for tiling but keep shower base only
Your picture from the internet is nice large shower with a square inside corner. Your existing shower is much smaller with a round inside corner, a real trick to set backer and tile for a novice tile setter. To minimize the round corner, you could go to "seat height" then set backer into the corner, but you will not be getting any larger shower, it will still be the same size as before, no way to enlarge it, the pan sets the size for the shower.

If you do wish to proceed, the base is typically a separate piece from the sides. It might come loose easily if the sealant does not grip too tightly.