I cannot erase a widget in header

Hi there,
On my webpage you can see a box in the header on the right side saying “Buche jetzt dein kostenloses Erstgespr?ch”. I read almost all the help pages on wordpress headers but I simply cannot find out how to erase that button or whatever it is.

Is there anyone out there being able to help me?
That would be awesome.

Thanks a million in advance,

Sarah

The page I need help with: [log in to see the link]