if you're getting troubles with the commands that's because The GM can't use all the Commands must be a PM, If you wana know how to use them just do like what khalidmadkour said
definition of a [GM] ="can trade any item" and run commands that "do not" change anything
definition of a [PM] ="can only trade items normally"... but "can run any command."
there is a reason to have both. a gm and a pm
a lot of people like to use both on the same account such as [GM]myname[PM] which will essentially give you a super user account that can trade anything and run any comand ... but is less secure than having two accounts