Do I need to undercoat this wall?

[Archiethere]

Hello, I’m looking for some help, if anybody could point me in the right dissection that would be great as I’m going round in circles online. We removed tiles from our kitchen wall the other day and half the wall came down, down to the bare brick. I’ve patched these however the wall is still quite uneven and there are bits of render missing. I believe the parts where the render is missing to be high suction as I’ve tested this a few times. Firstly do I need to undercoat this? If so would I have to use hardwall or bonding? Or am I completely off and I need to do something else?