Hello @Msk2000.we would like to add something more:
To answer your question individually, we would need to know what you would like to study and which Ausbildung you are considering to do. Also, it depends in which federal state of Germany (Bundesland) you want to study.
By law, dual Vocational Trainings (duale Ausbildungen) can be attended without a school certificate. After having finished the Ausbildung, you will have access to a University of Applied Science (Fachhochschule) and to Universities (Universität/Hochschule) in the same filed of your vocational training but only under certain conditions. You need to pass the Ausbildung successfully and have 3 more years of job experience in the same job.
If you want to study in any other subject, you need to get your German High School Diploma (Abitur) to access the university. Each federal state in Germany has its special school requirements and school types. There are different ways depending on your situation (Berufsschule, Abendgymnasium, Kolleg, etc.). This could be an option either while working or as a full time programme.
A good website to get more information, is the following: