Twenty seventee – headed image float

Dear all,

I would like to ask you for help. I am working with twety-seventeen theme. I want to edit behavior of the background image.
If I resize the size of the windows of the browsers, the theme image is cropping edge are towards the center.
I want to keep the right edge of the image still visible but this (freeze the right side):

.custom-header-media img {float:right;}
added to custom CSS does not work, as well as:

.has-header-image .custom-header-media img, .has-header-video .custom-header-media video, .has-header-video .custom-header-media iframe, .has-header-image:not(.twentyseventeen-front-page):not(.home) .custom-header-media img {
height: 100%;
float:right;
right: 0;
-o-object-fit: cover;
object-fit: cover;
top: 0;
-ms-transform: none;
-moz-transform: none;
-webkit-transform: none;
transform: none;
width: 100%;

}

I just found a way, how to freeze left side – it helps to delete width: 100%;, but I need to freeze right side.

I am pretty new to CSS, and because I did not find a solution for several days, I would like to ask you for help.
Do you have any idea, what to try?

Thank you.

Vilem

The page I need help with: [log in to see the link]