@Rain_Lover, I’m not at all sure what you intended to say because your post didn’t support your assertions, so please let me clarify my 2 points:
I looked at your post from the point of view of anyone who might be reading it from newbies through the volunteers here. It rendered quite differently from the image that you posted. Your request for assistance was not commensurate with your years of experience here.
Our posting guideline do not ask people to post snippits. We define, demonstrate and request a (1) “working page” or a (2) CodePen or a (3) Fiddle or a (4) link to your test site in that order of preference. A working page is preferred because with it we should be able to see what you see and how the code is written including the HTML and resource links in the head of the page. The working page gives us a complete picture of how your page is constructed and helps us answer your menu question most efficiently and even offer several choices if they are available. A clear verbal description of the problem is essential and sometimes a sceen shot or two can be helpful. Code should be validated before posting because invalid code cannot be assured to work consistently across the majority of devices.
Isolated snippits of HTML or CSS do not demonstrate your page and do not offer a suitable foundation about your intent. We often need to exchange several posts trying to glean the parameters of the request and often resort to guesses before we arrive at a satisfactory solution.
We expect members to have a plan in mind before posting and we help them get through their stumbling blocks. There are many courses available on the internet and in community colleges to coders who wish to expand their knowledge.
Your response to my post is puzzling because once again you posted isolated CSS without HTML. “Snippits” for which a reader is required to assume the corresponding HTML and who has no knowledge of the actual layout of your page or even whether it is responsive or not.
@coothead provided a “working page” that anyone at any level can read and use and @PaulOB posted a complete “CodePen”.
Please post working pages demonstrating your code so we can see what you see. Please explain the issue clearly. Do not leave others to assume unknowns about your layout. If you use Bootstrap or another framework, do include the links to the version of the framework that you are using, etc.
Help us help you. Doing that helps everyone else get the most out of your question and helps us provide an effective solution efficiently.