I still have some unsolvable problems with my frontpage. I really need help for having peaceful holidays

I made some screenshots due to my terrible english
Problem 1)

The module has the suffix frontpage. Whatever I change in css I can´t get rid of those gap between tabs and content. Whatever I change in .frontpage-css doesn´t have any effect of the gap there.
Problem 2)

How to get rid of those lines in content? Suffix clear doesn´t do the trick
Problem 3)

And still there is a problem with my header image. Slowly it´s driving me mad and steals my sleep.
How can I specify the proper height for the image without getting a gap between header image and content? When I set this:
#gkLogo.cssLogo {
background-image: url("../images/header_1410.png") !important;
background-size: 100%;
margin: 0;
max-width: 100%;
width: 100% !important;
height:160px;
}
i see the complete height of my header, but when I resize the window the content is going down and theres a big gap between content and header. Height:100% makes the header dissappear, same like height: auto.
The image resizes on smaller screens, but the missing height is only visible on small screens. Please please give me the proper code, I don´t want to guess anymore. I think I´ll never find a solution if you don´t help me. I think I´m trying to solve this mystery until next year if I don´t get the right code for the height of the background for my header.
And some more questions:
1. Is it possible to change the order of the boxes in mobile view? I´d like to see the tabs module a little earlier when I scroll down. I know I could make some modules invisible on moble, but how to change their order?
2. Is it possible to edit the mobile menu? In main menu I use a lot of Text separators for the "archiv content". Would it be possible to have a link only in mobile menu? In main menu a separator, in mobile menu a link to a small site with the links that are child links in main menu? In my case "Team, Topscorer and Spielberichte". My mobile menu is to confusing with so many links. Can I format some links bigger or smaller?
3. I would need a bit of help for making some content reponsive. Anyone here, who knows about divs? Only on two pages, I can use them as a pattern for the rest.
I hope I could get a little help before christmas. I can´t sleep very well when there are so many unsolved mysteries

But nevertheless I wish you nice holidays