As a student you receive from the government a package of 475 hours each year (your ‘quota’) during which you pay less in social contributions than a standard employee.
Use the Student@work application to can check how many hours you have left.
You are allowed to work for more than 475 hours, but the amount of social security contributions will be higher as of the 476th hour worked.
During the corona crisis extra measures have been taken regarding student work. Check all details on the page Coronavirus crisis: special measures for Student@work.