Thanks for your comments!!
Yes, there are many ways to do this. I guess, the most realistic way would be to create a well measured path in real life that has the exact same dimensions like my forest path. Then walk that path with a camera and track it, so that it can be imported into TG. The result would be amazingly realistic I guess. It's quite tedious, but maybe one day I'll do exactly this.
Another way I used before is to use an animated (walking) character in another app, Max in my case (even the mannequin figure in Max would be enough - it's just for the movement) and to bind a camera to his head. Like this you get a quite natural camera movement as well, which can be imported into TG.
I'll do some tests to see, what's possible...