I need to use posgresql as db, can someone provide any resoures or guide how to export identity.schemsa.json to posgresql schema

Not sure to understand what you trying to do

i need help to setup a DB connection with Kratos application

Hello. Why do you need to export identity.schema.json to postgres schema? Ory Kratos stores it by itself. You can find a configuration reference for docker-compose in quickstart-postgres.yml