Hi @ShelliOwo,
Thank you for your question and welcome to the Bunnings Workshop community, it is fantastic to have you with us.
There are two options you can consider depending on what is most important to you, convenience or space.
If you are looking for convenience, the easiest way to tile this wall without having to clean things up is to frame in front of the brick wall with either timber or steel, hang Villaboard over the framing and then tile over the new Villaboard. This will give you a flat clean surface to work with, but you will lose around 100mm of space in the room.
If this is not a viable option, you would need to replaster the wall. This would require you to clean the wall as much as possible to remove the glue and crumbling plaster. I'd suggest a Hyde 4" Plasterboard Joint Knife and Trojan 5x15 Row Brass Wire Brush would greatly help with the surface preparation.
Once prepared, you can plaster the wall using Gyprock CSR 20kg Hardwall Plaster following the manufacturer's instructions. You might like to have a look at How To Hard Plaster a Brick Wall for some guidance on the process.
You would then need to wait a few days until the plaster is sufficiently dried before tiling over the top.
You might like to check out How To Prepare For Tiling and How To Tile a Bathroom Wall for some guidance on this.
Let me know if you have any further questions.
Jacob
