My script does not sort right because the characters were assigned to Unicode code points in the wrong order. What can I do about that?
There is a misunderstanding here: Linguistically meaningful sorting is done not by comparing code point values (an approach which would fail even for English), but by assigning multi-level weights to characters or sequences of characters and then comparing those weights on each level. There are many algorithms and implementations for this; the standard Unicode Collation Algorithm (UCA) comes with a default weight table for all assigned characters as well as a tailoring mechanism that describes how this table can be modified to conform to local conventions, where necessary.
