"relation does not exist" trying to import mysql dump into postgres
This won't work. Don't even try feeding mysqldump output directly into psql. You'll need to dump schema and data separately, convert the schema either by hand or with a tool, load the converted schema into PostgreSQL then load the dumped data.

mysqldump's compatibility flags are moderately useful for dumping data but pretty useless for dumping schema definitions.

The "relation does not exist" error will be a follow-up error caused by a prior one. Try running with psql --set ON_ERROR_STOP=1 .... .