1. What is the basis of this business and the key point?
If your question considers the business of producing medical devices, the key point is to ensure the safety and performance of the medical device. The ISO 13485:2016 specifies requirements for a quality management system for organizations involved in one or more stages of the life-cycle of a medical device, including design and development, production, storage and distribution, installation, servicing and final decommissioning and disposal of medical devices, and design and development, or provision of associated activities (e.g.technical support).
2. How to start easiest and how can we understand 13485
First of all, you need to educate yourself about this standard. You can find some courses about it, find a consultant, and educate yourself with online articles. We recommend that the best start is to read our articles in the ISO 13485 Knowledge database which you can find on the following link: https://advisera.com/13485academy/knowledgebase/
This depends on how much time and resources you have. You can hire a consultant or you can buy a predefined documentation toolkit where all requirements are already described and your job is to and it is your job to adapt them to your processes, products, people, and more.