Norwegian letters, are fine in blogg post, but not in the blogg heading

https://www.teigen.be/blogg/?p=489

When i write in the post i can use characters like ? and ? , wich are special for norway. But in the header i have to write insted og ? aa, or instead off ? i have to write o.

If the characters do not show, her is a page that shows them: https://www.fotomagasinet.no/norge/

Any ideas how to fix this?