Gitlab CI/CD Integration

Hello together I tried to follow the tutorial here

to get AutoDevOps with Gitlab working, unfortunately without success yet. Gitlab is installed within the cluster it should use for devops. When trying to build the demo example according to the linked description Gitlab does not provide any error messages during configuration. Gitlab can connect to the cluster, as it is possible to install tiller and prometheus from inside gitlab into the cluster. However, for an autodevops enabled project Gitlab does not create a namespace like it is described in the linked tutorial and the build pipeline fails in the first build step with the following build log:

Login Succeeded
Building Dockerfile-based application…
Cannot connect to the Docker daemon at tcp://localhost:2375. Is the docker daemon running?
Cannot connect to the Docker daemon at tcp://localhost:2375. Is the docker daemon running?
Cannot connect to the Docker daemon at tcp://localhost:2375. Is the docker daemon running?
time=“2019-11-11T20:10:17Z” level=error msg=“Can’t add file /builds/cjohn/test/.git/objects/4a/8d7bae6f6d12746e4b760ab4fc9b89975a8300 to tar: io: read/write on closed pipe”
ERROR: Job failed: command terminated with exit code 1

Has anybody Gitlab integration working and could provide a hint? Thanks a lot for your help.

Best regards,
Christoph