How do request the correction of an incorrect spelling of a surname?
@Willisau, where do you see an incorrect spelling? If it is on a FamilySearch Family Tree profile, you can change it yourself. If it is on an indexed source, you may or may not be able to change it, just depends on if you can see an Edit link. Or maybe you are talking about some other area. You will have to be more specific about the details of your question.
I wanted to improve a list of location names and found, as sometimes before as I have ancestors from that region, that Hessen in Germany is always written "Hesse" without "n" at the end.
@D. Karp, that's because "Hesse" is the English name, and you presumably have your FamilySearch interface set to English. If you set it to German, many of this place's instances in Family Tree would change to the German name of "Hessen".