Well Done Leena for getting your pump and filter sorted, sorry not been around but my IP address frequently gets blocked by the administrator so I can't view the forum.

Carl your post doesn't make sense to me. Why turn to waste or is it rinse? before backwashing?
Waste setting bypasses the filter inside the multiport so just flushes water away (ok when vacuuming gunk directly out to waste)
Rinse puts the water through the filter in the correct direction, but pushes the water to waste rather than back into the pool as it could carry dirt but is used to re settle the filter bed after backwashing and before setting the valve to filter once more.

Domestic filters backwash quite badly so often take several minutes to clear the dirt from the filter, best to use a white piece of card behind the sight glass on the valve to actually see how dirty the water is but it can take a minute or two to expand the filter bed to a point where it starts to release the dirt properly.

Leena just over halfway is all the sand you need as the space above is to allow the sand be to expand during backwash without washing filter sand away as well.