Axon 7 Homescreen no Menu Button?

Hello,

i'm a little bit confused, but my ZTE Axon 7 does not show the menu Button.
I've only Telefon, SMS, Browser and Camera
It looks like this:

I'm missing the button with the 6 dots in the middle like it is shown on the first shot on the ZTE page.

I'm not new to android but new to android 6 and Axon7
How can i add it?

Regards
sonypsx