How much preparation time do I need before the March intake and should I continue working or quit my job in Germany?

You should start preparing for the March (Summer Semester) intake in Germany at least 8 - 10 months in advance. This gives you enough time to research programs, prepare for language tests like IELTS, gather documents, obtain the APS certificate (required for Indian students), and complete applications. Document and APS processing alone can take 2 - 4 months.

With your 5 years of work experience, you can continue working while preparing, using evenings and weekends for test prep and paperwork. You may need to take some time off closer to application deadlines (typically October - January), but quitting your job early is not necessary unless work prevents you from preparing.