Mark where the Shower screen fits on the tiles and remove the ridges
with an angle grinder with stone cutting wheel, and as said once fitted
seal with silicon.
Then remove bath and throw it away due to many scratches in the surface from
tile dust (even if you cover it well first!). While your doing this you may
want to remove the damaged tiles where angle grinder has slipped/grabbed and
retile as necessary! Plus if you ever need a new screen you will be stuck
trying to find one of the same, or similar, dimension for the wall channel.
DON'T use an angle grinder to do this. As we haven't seen your tiles it is
difficult to visualise the problem, but surely the ridges cannot be that
deep, use silicon as suggested after you have drilled the fixing holes and
are happy with the position. If necessary don't use the manufacturers
fixing holes drill your own to coincide with the tops of the ridges.