ᐅ Seal the large gap between the drainpipe and the brick wall

Hello everyone,

what is the best way to seal the large gaps between wastewater pipes and brick walls? During the bricklaying, large areas were left open where a wastewater pipe is now located. Also, every second brick has a complete hole through the wall because cutting the bricks was too complicated there. This is in an interior wall in the basement.
Can you simply fill these gaps layer by layer with mortar, or how is this usually done?
Thank you very much

Oriented strand board (OSB) is used there, which is then plastered.