Default [Q] Samsung Galaxy Tab 2 10.1 (root) 4.1.2, GT P5100 - No Navigation Bar anymore

Hey Guys,

sorry for my bad english..
I have a big problem and tried to solve it, but nothing worked.

My Tab 2 10.1 is rooted.
Android Version 4.1.2
Kernel 3.0.31
Touchwiz Standard Launcher

Since i installed some apps my status bar on the bottom is completely away.
I have no idea how it could happen. The navigation bar suddenly disappeared.

So i have no back, home, menu, screenshot button anymore.
Do anybody know how to fix this problem?
I can just go back via Webkey from my laptop.

Thank you so much
(i am very beginner and have no idea from all this stuff, but hope for help )))