Can I tile directly over this old adhesive (photos included) - Tile Advice

[amark16]

Hi all,

I removed some old tiles from the shower and wanted to know if it's possible to tile directly over this old adhesive. I removed some of it but it is a lot of work. I'm also planning not to tile the entire area that was tiled before but rather plaster and paint over it. So for anyone with plastering experience, will I have to remove the old adhesive, or can I place plaster over it and fill the gaps?



Many thanks!

 

[Samerlam]

From them pictures I would get the walls plastered before tiling