To change the logo, you can go to your Dashboard => Appearance => Customize => General => Logo, then select your logo.

To change the main menu, please go to your Dashboard => Appearance => Menus, select the Main Menu, then edit it.

To change the background color for main menu, you need to edit it in Dashboard => Appearance => Customize => Header => Layouts. = > Background Color.

 

To change the font for main menu, you need to edit it in Dashboard => Appearance => Customize => Header => Main Menu.