I don't have enough experience in MERN but if I've managed to make a couple of ribs.In principle I do not think it was necessary to make a BD for each company, I recommend reading https://www.tutorialesprogramacionya.com/mongodbya/detalleconcepto.php?punto=3&codigo=3&inicio=0 so you understand a little what I'll explain nextIn principle I do not think that it was necessary to make a BD for each company, in any case in the same BD creates a collection for companies and another collection for users, and the latter will "relation" them with their corresponding company. Then you as superadmin will load data in the collection companies mainly, and clearly also in users because you would have to define an admin user for each company.
Once you have done that in the internal logic you will have to define that for every company admin that loads a new worker will automatically take the admin company and relate it to that of that new user that generated it.For example: you will create the coca-cola company in the collection companies and a user called Pepito as Coca-Cola admin, then Pepito will have two attributes
name: nuggling,
type:admin,
company: Coca-cola (this will bring it from the relationship you defined from the collection users with company)
Then when Pepito believes new working users will read that he is coke tail so the new user will put him on coke tail.
user: josé,
type:worker,
company:coca-cola.This as an example, even for entrepreneurs you could create only a collection of users and there itself define their typical attributes as name, email, password etc, and mainly a company attribute and a type attribute, to know if it is admin, superadmin, worker, etc. Let's say the amount of attributes and collections will vary according to the complexity of your project.I leave you in case you need the documentation of mongodb to deepen https://docs.mongodb.com/manual/introduction/ All this of the DB must be defined in node with the help of a module called mongoose and the use of schemas, let you https://apuntes.de/nodejs-desarrollo-web/esquemas-en-mongoose/#gsc.tab=0 some mongoose and schemasSecond, for the management of api I recommend you to learn well nodeJS and the expressJS framework, learn the 4 basic requestspi Rest: get, post, put, delete, and then learn about routes.
I leave you some of that. https://juanda.gitbooks.io/webapps/content/api/arquitectura-api-rest.html to give you an ideawith this you can make a CRUD all by "console" say that you will not have graphical interface yet.I leave you a video that explains basicly how to make a basic CRUD from the express installation and creation of the api to the test of the operation with mongodb https://www.youtube.com/watch?v=DqpL5UtJHus Then you should learn something from ReactJs, at first understand the concept of components and properties, leave you a link to that https://es.reactjs.org/docs/components-and-props.html To then be able to do something basic visually and easily I recommend using a CSS framework to do it faster, like for example, materialize, I leave you some materialize https://materializecss.com/ Finally you must learn how to "joint" all of this, and to sum it up I pass a video that explains approximately how to join the frontend with reactJs to the backend by consuming the api you generated previously, the video to https://youtu.be/204v5QXHlmc
