Hi Annika,
Course templates and creating consistency for your learners are a great idea. You can backup and restore your dummy/template course to create a new course based on the structure you've set. For more information please see https://totara.help/docs/manually-back-up-a-course and https://totara.help/docs/restore-a-course-from-a-backup
You can also copy across specific items from your template course to a new course using the Import functionality - https://totara.help/docs/import-course-content
When I've created template courses in the past, I've included hidden labels on the course front page to offer instructions/advice to course creators/trainers using that template. They can delete these as required, but it can help with building that consistent learner experience.
Another thing you might consider is working through all the course activity and resource default settings so whenever a new activity is added to a course it has, by default, the settings/options you use most often.
Cheers,
Meredith