Composition is not working (no render, no file) I need a setup, where I render an object with transparent background but with reflection.

This is my setup (composition). The picture in the viewer is like expected. If I press F12 I get no file in the tmp folder and a "wrong" picture will be renderd (with plane). Compostion is activated, but its somehow ignored. Does someone has a tip?
To see result of compositing switch Layer viewer to Composite in Image Editor