Treat each wall individually rather than trying to tile the room as a whole.
How to lay wall tiles in a corner.
Installation of corner tiles is the same as it is for wall tiles.
Press the tile against the wall with the cut side facing the corner and the other edge next to the last full tile in the course.
Repeat the entire process again vertically before screwing wooden battens into place over the lines your starting point is the corner where the battens meet.
When tiling any wall you want the cut tiles in a less visible area than the whole tiles.
Step 4 lay the full tiles.
Trim and lay edge and corner tiles when you need to trim a tile before you lay it put the tile in place on the wall mark your cutting points and use a tile cutter or angle grinder to trim the tile to size.
Space the two tiles consistent with the rest of the tiles generally 1 8 inch which will leave a 1 4 inch space at the corner.
Therefore you should spread tile adhesive on the wall with a notched trowel and install the tiles.
As you work your way up from the bottom you smear your thinset onto the wall with a notched trowel depending on the size of your.
After you have finished installing tiles on one side of the internal corner you should continue by laying tiles on the other side.