Degraded picture of Great-Great Grandfather Can it be Fixed?

I found this picture of my Great-Great Grandfather and posted it to see if anyone can fix the damage.  The rules say "Describe what you want done" I will take any help I can get but my wish list is to have the; yellowing corrected, faces enhanced to see their features, scratches removed, and upper left corner filled in.  The Dropbox link to the picture is below.

https://www.dropbox.com/scl/fi/1n8rptlwcoird5mctatjb/Alexander-S-and-Martha-Porter-Family-Picture.jpg?rlkey=6exdhor62n05igrjyw93wuaw4&st=l1l1gzdh&dl=0