Disable LXDM and Start GTK Application

I try to start the Xserver manually after disabling the LXDM desktop.

After start up the ps ax | grep X shows me:

And after stopping the lxdm

When i try to start my GTK applikation, it fails because of “cannot open display: 0.0”

Then i tried to start the XServer like this, without any success. The login screen appears in the terminal.

Does anyone have an idea how to correctly start the display driver for a customer application?
Many thanks for hints and helping me with this issue.

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