Replace the wordpress theme header with another wp install header

Hi,

I have read about this a lot and still haven’t found a satisfactory answer so I am hoping you expert guys can help me:

I have a WP install at this address (let’s call it WP 1): http://www.charchub.com/en which as you can see has a black header; I have to note that the header and the menu use bootstrap so the header menu acts responsive changing into a three line menu on smaller devices.

I also have another WP install (let’s call it WP2) here: http://www.art.charchub.com which has a different header again using the bootstrap and is responsive.

What should I do to replace the WP1 header with WP2 header?

Keep in mind that I want to preserve functionality like responsiveness etc. The reason I want to do this is because WP1 theme has an absolutely crucial functionality that WP2 theme doesn’t.

Is there a way to make a bridge?