Calculate time difference in minute on SQL workbench J

I tried to calculate time difference between two time stamp column in minutes, but the timestampdiff function does not work on it, the error is telling me that “minute” column does not exist in the table I query, at same time some answers suggest that timestampdiff does not work for postgresql, but postfresql function like date_part does not work on my end as well, could anyone share experience or any document for the grammar and function on SQL workbench J? Thanks!