Hi, mariuszdh, welcome to the SitePoint forums.
I like the way your drawing depicts the issue. 
Very well done, sir.
To help with the issue, we would like to see a working page that demonstrates the issue. Do you have your code set up on a test site, by any chance? That would be very helpful if you do. Otherwise, can you assemble a working page and include it with your next post. Just remember to try it on a separate computer or separate drive to assure that it will work properly… on our computers before posting it.
If you have not done so already, please read our posting guidelines for a detailed description of a working page.
Forum POSTING Guidelines (Posting Basics): (Help us help you!)
Forum Posting Basics
The code needs to be complete and accurate to work properly. Validators for checking the HTML and CSS can be found here:
https://jigsaw.w3.org/css-validator/
Looking forward to hearing from you.
Cheers!