How can i change user in postgress trminal?



Hi, i need help, im trying to create table in postgress but when i am typing psql, at the start of line i have ubuntu=#, not postgress=# how can i switch to postgress=#?
when i typing sudo -su postgres psql template1, it s ask password i try ubuntu, ‘’, and accout pasword not working.
i try this Super user (root) in terminal, but i think it s not best solution.

and i still cant to create database :frowning:
I will be very grateful for your help.