How to fix my Bosch classixx dishwasher?

Pump is not working. So water not draining away. Have emptied water and checked filters, all clean and OK. Turning machine upside down and removing the inspection panel I see there is a reservaoir full of what looks to be a dirty mess. Made of plastic and it looks as though the top can be removed. Is this the case and how do you do it, please? Engineering and electrics I understand.