To fix Bathroom wall tiles, start by removing any damaged tiles with a grout saw and chisel, taking care not to harm surrounding tiles. Clean the area thoroughly, ensuring it's free of old adhesive and debris.

Prepare the tile adhesive according to the manufacturer's instructions and use a notched trowel to apply it evenly to the wall or the back of the new tile. Press the replacement tile into place, using spacers to maintain even grout lines, and adjust as necessary to ensure it's level. Allow the adhesive to dry for 24 hours. Next, mix and apply grout with a grout float, pressing it into the gaps around the tiles. Wipe away excess grout with a damp sponge and let it set for another 24 hours. Finally, apply grout sealer to protect against moisture and stains, and clean the tiles with a damp cloth to remove any residue, ensuring a durable and professional-looking finish.