Ok just going off that picture you have no chance or getting the manual as theres no markings on there to make out what it could be. Also Technik went bust a few years ago so all the manuals went with them so you wont get any Technik support manuals im afraid.
But looking at the oven its just a very basic oven with only a few settings on there so you don't really need a manual for this. I can explane what the settings are for you so you can write them down for the tennent.
If you select the oven setting and go clockwise round its as below.
First setting is a defrost setting which only gets warm to around 50 degs so this setting no one ever uses.
Next is the convection oven on its own.
Next is convection oven with a fan so it gets hot a bit quicker.
Next is full heat grill
And last is low heat grill.
And the dial on the right s straight forward the temperature setting.
So the main settings people ever use is the full grill and the oven setting.
Hope this helps. If you need anymore info just get back to me.