Waterproof Tub

Waterproof Tub
Can a tub surround be cut or bent to accommodate a protrusion due to the sloping roof above the building stairs?

I I live in an old house where the bathtub in the corner. Unfortunately, the protrusion of the attic stairs above, is approx. 2 feet from the corner of the tub wall and 3 feet above the rim of the tub. This forms a 45 degree wedge angle bump in the wall of the tub back to the ceiling. I would like place a tile tub surround look, but the only way I can do this is to cut around and try to join it to adapt to possible double angle.Or 45 Part. But it has the side of the pons to deal with. I know I could shingle, but prefers not to. I can not move the tub. I had found something called AquaTile, which is supposed that is water resistant tile board, but do not know how well it would work well. Any suggestions anyone has to know how to bring this and other materials that can work would be greatly appreciated. I hope this made sense, because it is very difficult to describe. Thank you very much.

They sell plastic channels The Home Depot, Lowes etc., which is crazy and specifically for these tubs … It is a narrow strip close to slip into slots on each side .. cut sheet and then the channel has a slip on the edge of the tub right back cut in the same on both sides .. slide by about 1 / 4 inches and are waterproof, made specifically for situations like this.