>hello how are you, I need your help, I am trying to make a multi-company system but based on different data, how can I do it from a screen with all the companies the selected application is executed and after leaving that application I will return to the screen of the companies and to be able to execute any of the companies with only to put user and password only once

This is a very complex question with many potential variables. I'm curious to hear what other people give you in the way of guidance.

Generally speaking, each company would be in its own database. You would open the database in that company's directory. If you have shared resources that are distributed among all the various companies, these can be in another database.

How your login and access system operates is dependent upon your design goals. You can set it up a multitude of ways. For most of our apps, we use folders with complete systems, and each user must log in whenever they access another company's data. If they go into prior year archives, we have a system setup to automatically honor their current login in the current year so they don't need to log in to prior year data (because they may not have been a user back then, but were only hired this year, for example), so it just goes in without the test on archive data, and the same in going back to current data. But whenever they access another data set in another folder, a full login is required.