"All Germans shall have the right freely to choose their occupation or profession, their place of work, and their place of training. The practice of an occupation or profession may be regulated by or pursuant to a law."
According to article 12, all German citizens are free to choose their profession, vocational training and workplace. No one can force an individual to learn a specific trade, study at a particular university or take up a specific job. However, there is no guarantee that you will manage to get the desired vocational training spot or job position.
Article 12 pertains a civil right, so it only applies to German citizens. Citizens of other EU countries also entitled to freedom of occupation since it is stipulated within the EU law.