Travelling to mumbai for first time, saftey tips, precautions to be taken ?

Mumbai is a big city and there are different kinds of people. If you are visiting for the first time, I would suggest you not to trust anyone blindly. Choose your accommodation after a bit of research. Ask other people' review about the hotel. You should definitely avoid street food if your health does not allow it. You can taste Mumbai's specialties like Vada Pao, Batata vada etc in cleaner areas as well. For shopping, here's a reference for you