Problems with custom theme: logo and main menu on smartphones

I have 2 problems with my custom theme:

I can’t display our logo. It displays well when I enable the CERN theme instead.

The main menu doesn’t display correctly on smartphones.

The site is

As it is now online, I have tried to comment all lines in my theme.css file on the dev version ( to check that it was not related to the code in it.
Thank you for your help,

I have installed a second custom theme without any special theming at the moment and it displays the logo and the menu correctly. I will try to add my customizations to that theme now.

Hello Jan,

By custom you mean the override theme?

I copied my theme.css file and my patterns folder to the new theme and everything works now.
I should have tried that before, sorry.

Yes. It’s solved now. Thank you.