Canno't mount and run database with Docker Composer

Hello ,
I'am trying to mount database inside volumes on docker composer and then I didn't know how to run this image Odoo with database gived on volumes.
I had already mount extra addons gived on the docker composer but canno't mount database which gived on the docker composer .

=> For more details these is my docker comopser (my database is located on my git project + docker composer )
(/dpbox_db contains the db on git project )
Docker Composer File :

version: '2'
services:
db:
image: postgres:9.5
environment:
- POSTGRES_PASSWORD=odoo
- POSTGRES_USER=odoo
- PGDATA=/var/lib/postgresql/data/pgdata
volumes:
- ./dpbox_db/:/var/lib/postgresql/data
odoo11:
image: odoo:11.0
ports:
- "8076:8069"
tty: true
links:
- db
depends_on:
- db
environment:
- PGHOST=db
command: -- --dev=reload
volumes:
- ../extra_addons/:/mnt/extra-addons
- ./o_etc:/etc/odoo
volumes:
db:
odoo11:

Please Help to solve my problem thanks .

Cordially Turki Makki.

Start with the Docker Compose file in the issue, especially the db service's ./dpbox_db/ mount and the PGDATA setting, then run the Compose setup and inspect the database container logs. Done means the PostgreSQL service starts from the project database volume and the odoo11 service can connect to it without errors.