The first very important step is to get a wider ranger of colors in the picture - with
photoshop's colorbalance function (CTRL+B):
Shadows:
__cyan-red:-15
__magenta-green:-10
__yellow-blue:+35
Midtones:
__cyan-red:+40
__magenta-green:-20
__yellow-blue:-45
Highlights:
__cyan-red:+30
__magenta-green:-10
__yellow-blue:-100
For the next step i used the "Color Efex Pro 2" plugin from "nik":
Filter -> nik Color Efex: traditional filters -> Bi-Color Green/Brown...
Basic Tab:
__Select Color Set: 1
__Opacity: 55%
__Blend: 90%
__Vertical Shift: 60%
__Rotation: 160%
Advanced Tab:
__Protect Highlights: 0%
__Protect Shadows: 30%
Then i used the Curves-tool to make it a little brighter(CTRL+M):
Input: 120
Output: 140
In the last step i set a new whitepoint with the Levels-tool(CTRL+L):
finish
