If the dishwasher isn't washing as it should, let it fill and start spraying, open the door and check the water quality. You could have too many bubbles (from soap), very dirty water, or left over food. If you have any of this you can try to clean the filter and/or fill and drain until the debris is gone (especially with bubbles). If the machine still doesn't clean well, you may need a technician to clean the pump out properly, or even replace the pump in some cases.

Make sure you are following the proper loading procedures, including proper type and amounts of detergents. Run the unit through cycle while empty - if it doesn't leak, it's probably a loading problem.

Make sure the racks are positioned properly.

Make sure the door is unrestricted around the opening.