Whether you face personal problems, think the programme is not as described, or do not feel comfortable in your current job.
First and foremost, you are allowed to leave an apprenticeship at any moment. It’s the same as if you were in a regular job; your contract will stipulate how much notice you must give your employer if you wish to leave.
However, it is critical to realise that you will not get a certificate if you leave your apprenticeship before it is finished despite possibly completing considerable work. This is something you should consider before making your decision.