How do I decrease the row or column height?

Hello!

Currently my header has no search function and looks like this:

I want to put a search on the right side of the header, to the right of the main menu, and I want it to look like this:

Currently the header I’m trying to make look like shown in picture 2 looks like this – in the red lines is a row:

The blue lines are the column:

On the left side of the column is the main menu:

On the right side of the column is the field with the search button:

How do I decrease the row or column height?

I tried to decrease the height of the row or column as shown in the picture, but I can’t decrease it, I can only increase it. What do I need to do to make my header look like I want in picture 2?

I hope you can easily orientate yourself from the photos, what needs to be done.

Thanks!

Thank you!!!!!!!!! 😉