individual start page for WPTouch disable Mobile/Desktop

Is it possible that on mobile devices a individual start page is shown instead of the naked one?

It is unclear what you’re asking here. Please try again so we may assist you.

I want that when WPTouch is choosen a static page will be displayed.

A mobile landing page can be set using Core Settings > General > Landing Page.

Is it possible to disable the Mobile/Desktop switch?

The theme switch may be hidden using Core Settings > General > Desktop / Mobile Switching > Show switch link in mobile view. This is an advanced setting so be sure to view your admin panel in advanced mode (set under Core Settings > General > Admin Mode.