I’m struggling granting permissions in PostgreSQL being used mostly to MariaDB.

In MariaDB there is an easy console statement to grant all permissions on all tables inside a specific database to a specific user:

GRANT ALL PRIVILEGES ON ex_database.* TO 'ex_user'@'localhost'; FLUSH PRIVILEGES;

With this the user is granted to do all table operations inside that specific database.

I saw that granting all privileges on a database was different in PostgreSQL (e.g. postgres 8.4 – grant privileges) and there should be a way with using schemas (e.g. /a/24410344/5621032) but that doesn’t seem to be restricted to a single database?! And how do the schemas even work? Do I have to set these up for every single user?
Isn’t there an easier way? This feels very complicated.

I’m looking forward to the explanations hoping that this will help other “transferrers” from MariaDB to PostgreSQL. Thank you.