partly I had this problem as soon as I modified the configuration file
subsequently I reset all the default values ​​to configure the database from the browser but nothing
I uninstalled odoo and reinstalled but still nothing

Hi,

Check if the configuration is correct,Check the odoo.conf file

[options]
; Is This The Password That Allows Database Operations:
admin_passwd = admin
db_host = localhost
db_port = 5432
db_user = odoo15
db_password = False
addons_path = /home/user/odoo/addons
xmlrpc_port = 8015

For more details, refer to the blog:

https://www.cybrosys.com/blog/odoo-15-development-environment-using-pycharm-in-ubuntu-20-04

Hope it helps