I have a business and a lot of costumers sell they're products on my site. And now i want to give a permission to some of them to see and analyze the data of their products.
Can i give them a view permission for only one page or for only one segment?
Yes, you can create a new View and set up filters as you need.
See GA support about filters: https://support.google.com/analytics/answer/1034823?hl=en