Hi Mikol-
The specific answer to this question will depend on the theme you’re using. I checked out the site you sent over privately and it looks like you’re using Crio, so this is going to be easy to fix.
Right now, you have your header set up with 3 columns— Your logo on the left, your menu in the middle, and an empty branding section on the right.
Navigate to Customize > Design > Header > Layout and look for the empty column, and click the trash can icon to delete it.