All Puppies will want to explore their environment and Giant Schnauzers are no exception. It is vitally important that you recognise this and plan for the safety of your puppy, just as you would a human toddler. You should consider whether its permitted area is escape proof, whether there are things like mains power cords it can chew through, whether there are unprotected fires or heaters and generally what other potential hazards are presented by its play area.
You can mitigate the risk by employing a creche, shown in the photo, but as your puppy gets older, it will want to explore further afield.
Your precautions should also extend to your garden as you will inevitably want to take it out, especially for toilet training.
You will want to make arrangements to confine your puppy when you need to leave it while going shopping. A crate or chreche offer the most practical solutions.