how can i fix my dishwasher Ignis ADL 348 items always dirty?

the plates and cups in my dishwasher always come out dirty. We have cleaned the filter but dont know how to do anything else as our manual is in italian. what do i do with the salt dispenser in the floor of the machine has that anything to do with it. Also the dispenser in the door next to where you put the dishwasher tablet whats that for.