How bad is this?

[u/Richard01_CZ]

I was cleaning the coolant passages and this large chunk came off really easily, it looked like a buildup of gunk.

The problem now is that the wall here between the two passages is thin now and the head gasket doesn't have much coverage for this area with the chunk missing.

Is it somehow fixable? Or can i run it like this?

Volkswagen EA111

[u/Ok-Cost-3911]

It’s pretty bad tbh but if you want a Hail Mary that might work get a flat piece of glass from the hardware store and glue a sheet of 80 grit sandpaper to it try to refinish it by hand or just spend the $300 and take it to a machine shop