As soon as it starts filling it starts draining and never fills?
You will want to check your drain to ensure that it is not shoved too far into the standpipe as this issue sounds like it is a siphoning issue that is occurring.
Is there a way to adjust the water level. it seems as though the water does not come up high enough when it is set on the highest level
There is no way to adjust the water level for your washer. The water level should come to a couple of inches below the inner tub balance ring.
When I put it on spin to drain water out. It leaks water out at the top rear of drum. On full or medium level.
You will want to look for a restricted drain pump that would cause the unit to not drain fast enough and allow water to overflow the tub.