Inefficient queries are queries which take a long time to complete. Such queries could occur if the database needs to analyze a lot of different tables and rows in order to fetch the results.
There is no generic way on how to approach this problem and we don’t have logs to help you figure out which queries cause it. It’s usually caused by queries which search a lot of rows and don’t use indexes properly, and could be caused by a bad script or plugin.
However, to get an account reactivated, you need to submit a review request through the client area.