Hi, when I added a new forum skin I smashed up on.
It's about lying can not delete the original bluish connection header.

What kind of skin have you added?
How did you add it?
What do you mean by "connection header"?
Is this post related to miniBB?

I do not know how to remove ie those which overlap each other on the background (the standard blue)

The screenshot:

Well, it's something we have by default. Do you see it on top? The yellow panel overlaps two backgrounds of the certain height.

You just need to edit templates/main_header.html to place menu in your own table or div.

There is only how to remove the blue background of the image?

Edit templates/main_header.html.

Blue background comes from class which may be undefined. Without seeing the source of your page, I can't tell exactly what class name.