Tell me how to organize safe sales and payment through the site?

This is only through individual software development with a good degree of protection. You can contact the Software Development Company https://tech-stack.io/services/back-end-development. The company knows how to turn your ideas into software systems and processes that optimize the efficiency of your business.

A great way is to use CRM. They are used successfully by many companies and help to increase both productivity and profit. More information about creating custom CRM find in the article: https://requestum.com/custom-crm-development