how can lower or increase ( width/height ) on the page header featured image

You can set "Resize image" to true and set a height: https://generatepress.com/knowledgebase/generate-page-header/ (first image).

i go to image section>>> resize image enable>>>>image height i set 1400 px
and still doesnt work .
i saw the video and still i am stuck :)

i dont have any content inside
could this be the problem ?

does not work even with content inside

1400 is pretty massive for the height of an image.

Can you link me to the page?

in your video you upload an image more then 1400 px height
and it works like a charm .
but even when i change it to 400 px nothing happen !
and i cleared cache .
see the website
http://www.buildingawebsite.co.il/

Ah, cropping it only works if it's a static image - not an image background.

When using a background image, the height is determined by the height of the container.

In your case you have the page header set to full screen, so the image will resize to fit the screen.