The quickest way is to use a commercial mastic remover.
Taking tiles off stud wall.
Usually the remover is applied to the remaining clumps of adhesive with a rag brush or sponge then left to sit for a few minutes.
Remove the grout first.
Break the tile if necessary.
Slide a putty knife or plaster spatula behind the tile getting as much of the blade behind the tile as you.
This approach should let you save more of your tiles for reuse unless the tiles are.
How to remove bathroom tile without damaging the plaster walls step 1.
Scraping away grout between the tiles is the first step in removing them.
Tiles installed with thinset or another tile adhesive often require more work to remove them.
If it is how it is repaired depends on how the wall is constructed.
Work slowly and at about a 45 degree.
If the wall is a proper stud wall then the new plasterboard can be fitted over the original studding.
Once the tile is down take a 5 in 1 tool and scrapper to remove any excess grout.
Wedge the end of a putty knife beneath the bottom of a tile and gently pry outward.
The method used to attach the tiles to the wall affects the way the tiles come off.
Try to locate a loose tile.
With the removal of the one tile keep going under the surrounding tiles gently popping the tile from the wall by prying it from the wall using the scraper and hammer.
Chisel tiles away from the wall.
What you need to know.
Dissolve the tile adhesive which is also called mastic.
Cut away the grout surrounding the tile or tiles that you want to remove.
You may be lucky and the tiles will come off without damaging the wall too much.