1. Login to the WordPress dashboard
2. Open the website in site setting mode.
4. From the header size part, you can see 4 options:
Header width:
Change the whole width of the header
Header Height:
Change the height of the header
Container Width:
Change the width of the header's container
Top Space:
Increase or decrease the space of the header from the top of the page.
Also, you can change the size of the logo, navigation menu, notification icons.
Just put the mouse cursor on the place which selected from the below image and pulls it to the right for increasing the width and pull it to the left for decreasing the width of the elements.