Hamburger menu problem (Booster / Multitheme)

Hello all,
I've got a really important question (who will be decisive for my graduating thesis)... My website's on booster theme and I used multitheme for the homepage (thanks @espenmn) to install a countdown... My problem is that now, the hamburger menu of my homepage doesn't work. nothing happens when I click on an item.
If I'm on another page , the hamburger menu works: there's an animation on the item and I'm redirected to the good page...
How can I fix this please?

I totally uninstalled multitheme for testing and that's not the problem. So the problem comes from booster.
That's a big problem because the users cannot access to other pages than the homepage if they're on smartphone...

Hi… I have been away for a few days but I think there are a few misunderstanding.

In general:

  • In Plone, you can only have one theme enabled at the same time.

  • If things are made correctly, having a theme installed and not activated will not 'matter'. The other themes that are installed but not enabled should not 'do anything to your site'.

  • You can customize your theme and copy things from other themes. If you do that you might have to copy/edit CSS (or javascript) to get the 'features to work'.

I've found an answer... There's a problem in the Booster theme css, the title is set as a display:table cell and it completely blocks the hamburger menu...
Who could I contact to give the CSS I wrote to fix this bug?