How can i mend my Bosch SCS 4012 GB/14 Dishwasher?

Which ever programe the machine is set on it starts to make the noise as if the pump is working but it does not fill with water.
On the occasion it does start to fill up, usually after the machine has had a good shake, it does not finish the process and never even dissolves the dishwasher tablet.
There is also a leak because the bottom door seal is faulty, it is not ripped but will not stay on the lip at the bottom of the door.