RaspiCam on RPi 1 B+ doesn't show images

Question

I'm trying to get a livestream with the official raspicam (with IR; revision 1.3) working, which is attached on my Raspberry Pi 1 Model B+.

The problem is, that I get an gray screen when I'm accessing the camera-stream via webbrowser and it gives me the following error message: UNABLE TO OPEN VIDEO DEVICE ---- ERROR CAPTURING FIRST IMAGE

My webbrowser shows the following:

Here is what I already tried:

• I already installed motion and configured it like in some tutorials. The configuration file is here: http://txt.do/dzget
• When I run raspistill -v it does display a live image on my screen, so the camera itself works.
• I also did the command (and put it into autostart): sudo modprobe bcm2835-v4l2
• There is also an terminal named /dev/video0.
• I already uninstalled fswebcam and ffmpeg as suggested by some forum posts.
• The GPU has 256 MB memory.
• The folder which should contain the motion images is /srv/motion, but it is empty. The permissions are: pi@raspberrypi:~ $ ls -l /srv drwxr-xr-x 2 motion motion 4096 Jul 7 13:44 motion

When I view the output of the motion service, there is nothing / it does nothing:

    pi@raspberrypi:~ $ sudo motion -n -c /etc/motion/motion.conf
[0:motion] [NTC] [ALL] conf_load: Processing thread 0 - config file /etc/motion/motion.conf
[0:motion] [NTC] [ALL] motion_startup: Motion 4.0 Started
[0:motion] [NTC] [ALL] motion_startup: Logging to file (/var/log/motion/motion.log)

Could it be possible, that Raspian Stretch isn't compatible with this old camera or Raspberry?Does anyone of you know a solution to my problem?

Thank you for any help!