Question: I am starting my App from XCode and with a specific behaviour it just disconnects and the app disappears from my IPAD screens. 
So I guess the app crashes.

Now my question. Where Do I get this crashlog ? I already looked into 
Window -> Devices -> choose my Ipad -> "View Device Logs" . But I cant see any actual crash log. I have some from earlier times, but my actual doesn't show up.

How do I get a crashlog ?

Answer: 
check if you have enabled Share with app developers option in settings. Privacy -> Analytics -> Share with App Developers.Xcode was not showing crash logs, enabling this helped me
You need to look at the device console under windows, devices in Xcode.

Its possibly saying something about code signing, bundle id's or missing libraries.