Css problem in the menu

I don’t know what is exactly happening, but the menu doesn’t display properly, see below:

I did a component including the website logo.

To make each item looking as bottons, I did as usual: some padding around the text, but it doesn’t work properly.

In the backend I have something stranger: When I load the header, the problem appear, but when I change the value of the padding it looks normal, but not on the front.

after changing the padding value: