Patch tiling onto plasterboard after new shower

Need help. I’m princess of having new shower fitted. Need to tile where work has been done. Gap filled by plumber with plasterboard. Is it ok to tile straight onto this.
Done but if research on here and other sites and was going to use mapei-primer-g-water-based-synthetic-resin-primerto prime and mapegrip-d2 adhesive. Will need approx 4 sheets of mosaic tiles

would like confirmation I’m using the right stuff (times like this girl needs her dad he did all this sort of stuff for the family)

photo added of work to be done

cheers folks