In ".gitlab-ci.yml", use "include: .gitlab/ci/jobs/windows_jobs.yml".
Found errors in your .gitlab-ci.yml:
- deploy_branch_on_windows: unknown key in `extends`
04.06., 9:00 - 12:00: GitLab will be migrated to a new server environment and upgraded to Enterprise Edition Ultimate. The estimated downtime will be 2-3 hours. Please see https://doku.lrz.de/display/PUBLIC/GitLab+Ultimate+Migration for more details about changes related to the migration.