Are the scratches really on the emulsion side or are they on the base
(back) of the film?  If they are on the back, then a temporary fix, that
is, each time you print the negative, is a product called No Scratch by
Edwal.  You clean it off after each use.  Or you can use the old
photographer's trick -- nose grease.  Rub a little of the oil from crease
between the side of the nose and the cheek into the scratch.  Both these
techniques work because the index of refraction of both are the same as
that of the acetate base of the film, and greatly reduce, but don't
eliminate, the projected image of the scratch.

Now, if the emulsion is truly scratched, then you got real problems,
because the actual image is damaged or if the scratch is all the way to
the base, the scratch has removed that part of the emulsion and, thus,
the image there.  The usual "fix" for this is to fill in the scratch so
that it prints white, retouch that print, and make a copy negative of it.
Retouching directly on the negative takes the hand of an experienced
negative retoucher.  Trying to do it yourself would probably fail and
you'd ruin your original negative, even if the scratch were retouchable.
If you want to try, I suggest that you have a pro lab make you several
contact, duplicate negatives to retouch on, then if you screw up, you
haven't ruined your original.

The major makers of retouching supplies is Marshall, Edwal and Spotone.
Sorry, I have no links to their web sites, but most high end photo and art
supply stores carry their products.  

The ulimate, and probably the best, solution would be to use digital
technology: scan the negative(s) at film resolution, digitally retouch it,
and have a new negative made from the digital file.  Expensive, but you
would get a negative without defects, that is as good or better than the
original.

Stefan