First of all remove your detergent tray ... get an old tooth brush and clean every nook and cranny where old detergent sticks.
Open up your door, and separate and inspect your rubber door seal ... lurking in the crevices you more than likely have spots of mould... once again give this a scrub with the toothbrush using mould remover, or some other cleaning agent.
Then remove your filter and see what you have trapped in there... there's usualy something in there, that you would rather not touch.
Clean it out an re-fit the filter.
Finaly put some soda crystals in the detergent tray and let the machine do a rinse cycle ... just follow the instructions on the packet.