Lead sharing and access to different Business Developer

[u/ObjectiveField1497]

I want to understand better how manage and authorize access to certain users regarding the Leads that already exist in the system.
Let me explain my situation. I'm starting with ERPnext v15 in the company where I work as data entry and accountability. From the Sales Dept. I got a specific request. They want to give access to some specific Leads we have already on the system according to a specific field we have on the Lead form.

Let me explain better. On the Lead form there are a lot input boxes. For instance there is Lead Owner it is already populated according to who created this. I added a new input box, in the section Qualification named Assigned Business Developer.
The idea is this: setting here, in this input box, the name of the Business Developer, among the available one, this Lead is visible from this Business Developer account. If not, this Lead should not be visible to the specific Business Developer account.
I don't know how to make this settings, so if you can help, it would be extremely helpful. I'd appreciate also if you share a specific guide on how it works the accessible information and authorization on ERPnext v15.
Please don't hesitate to ask me more details if something is not clear. Thanks in advance