Postgresql arbitrary queries

I have pgAdmin 4 and PostgreSQL 10. I can't execute a query without quote marks i.e. I want to excute this select * from table but it only works if I use select * from databasename."table" How can I remove this restriction? The name of the table is Complexitie. I was using postgresql the last year and I remember I could write queries in a simple way without mandatory syntax things like case senstive, mandatory quotes. I read something about to setup arbitrary SQL queries en Postgres, but I can not find steps to configure it. thanks