landing page --> menu should hide by default, but appear when scrolling down

This is the site we are talking about right?
http://www.fudiggl.de/

I'm seeing a jQuery error which likely causing the issue. The mobile toggle isn't working either.

Can you disable all plugins except GP Premium to eliminate any plugin conflicts?

Please disable your custom functions if you have added any as well.

Let me know :)

It has to be a css error! As soon as I activate the "simple css"-plugin, the errors appear.
I try to figure it out, now that it's focused...

Perhaps you have a tip: in mobile view I can tap the "menu" and the slide-in-menu opens but: without any entry!

I can't get your site to load currently.

It's not a CSS error as I saw js error in the console tab before.

That's all the css code concerning menu. What's wrong?

/* hide header on start page */
.page-id-4892 .inside-header { display: none; }

/* bring menu to the top */
.main-nav, .main-navigation, .inside-navigation { z-index: 108; }
.main-navigation.navigation-clone { z-index: 108; }

/* colored line below menu */
.main-navigation { border-bottom: 3px solid #a00000; }

/* hide menu on start page and show when scrolling */
.page-id-4892 .main-navigation { display: none; }
.page-id-4892 .main-navigation.navigation-clone { display: block; }

I can no longer get your site to load.

It's not a CSS issue as mentioned above.

I saw a js error in the console tab before and most of the time it's because of another plugin.

Have you tried disabling all plugins to test?

Let me know if you need more info :)

I have deactivated any plugin, the error occures as soon as "simple css" is active...

I kind of solved it on mobile with "media":

@media (min-width: 789px) { .page-id-4892 .main-navigation { display: none; }}
@media (min-width: 789px) { .page-id-4892 .main-navigation.navigation-clone { display: block; }}

Can you point me to the js error you mentioned above?

It really can't be simple CSS as it doesn't use js.

This is the error I'm seeing:
https://www.screencast.com/t/j7TiyOtuU

Unfortunately, I can't tell where it's coming from which is why disabling all plugins except GP premium is step 1 in debugging procedure.

I don't see that JS error: https://www.screencast.com/t/kBmp6Esa

But: on my start page the menu appears by default! It should hide by default and show up when one scrolls...

Weird. We are talking about this site still?
http://www.fudiggl.de/

Yes

I'm on another computer and definitely still seeing that error.

Not sure why it isn't showing up to you though.

Can you please disable all plugins except GP Premium so we can try to identify the error?

Let me know :)

I don't see that js error... how should I know, which plugin causes the error, when I don't see one?
;-)

I'm not sure either but I really don't have other ideas on how we can go about this.

Is the mobile menu toggle working for you?

If not then can you disable all plugins and see if it starts working?

We need to start somewhere :)

when I set sticky-effect to "glide" the menu doesn't show up on non-mobile at all...

Unfortunately I really can't tell you the reasons why it isn't working without some basic debugging steps.

Can we please start with all plugins disabled except GP Premium and temporarily removing all your custom CSS and functions?

We really need to take one step at the time to solve issues like this.