Create a website with admin and user side

Hi, I would like to have a website where we offer our service to other companies and individuals. Our goal public is companies, not individuals. These companies can login and I can give a discount code to these companies. When one of their customers uses that discount code for an offer or for a confirmation, the companies can see an overview of all their users that used their discount code. When one of their users confirms with the discount code, the company itselfs gets 15€ credit. Let's look at an example: There is a company ABC who offers our services to their customers. They don’t actually do that service but count on a contractor (like us) for this service. They tell their customers (X, Y and Z) to ask for an offer on our website (contact form) with the use of the discount code “ABC123”. Then users X, Y and Z each receive and e-mail with an offer for this service. On this offer (a pdf file), the discount code is mentioned together with the total price of our service. There is also a unique number on the offer, which will be the projectnumber. When the users X, Y and Z confirm the offer (on our confirm form) where they enter the discount code again, the user receives the discount, the project will be added to the portfolio of company ABC and the company ABC receives a credit of 15€. The users X, Y and Z receive an e-mail with information. The company ABC receives an e-mail with the notification that a user of them has confirmed our services. I receive an e-mail with the notification that a new user has confirmed an offer. The service that I do goes in two parts. When part 1 is done, I upload the pdf file on the platform. There I have the ability to press a button “Send”. The user then receives an e-mail with the pdf I uploaded. I can also generate an invoice, a pdf file is created. Again, I have the ability to press send and the user receives the pdf invoice (that bills 70% of the total) via e-mail. Same for part 2. When part 2 is done, I upload the pdf file on the platform, click send and the user receives the pdf file. I generate the invoice and click send. The user receives the invoice. In attachment I have created an example of how I would like to follow up on projects. It's very visual to see which projects have been done. The company ABC can only see things. It can see that they have two users (X and Z). They can see the pdf files of these users. And the can see their credit. User X can only see pdf 1, invoice 1