/diy/ - Do It Yourself

How do I clear the pipe that goes into the wall? As soon as the trap at the plug fills the water starts going up the sink.
I've tried removing the plug and going at it from below but the angle is too steep. There is a grate at the bottom of the sink I didn't draw so it's hard to get anywhere from up top too.
Pouring cleaning fluids or hot water in the sink mostly traps it at the plug so it doesn't seem to do anything about the blockage.

How do I clean the shit stuck in the pipe that goes through the wall?
If I let the tap run for a few seconds, not even full blast, it starts filling up the sink. I've cleaned all I can from below by loosening the screw plug but it's not the issue. I can't reach inside the pipe with anything to get to the gunk. I've tried some mild solvents and hot water + plunging the shit out of it with all the holes plugged up to no avail.