Create analytical accounts for branches and select appropriate branch name (analytical account) when creating sales or purchase orders or invoices. This will enable branch wise sales and purchase statistics generation.

When you talk about multi company it is about the time that you want separate system for each company, but for some other actions you can use various options. consider you want all the data in one accounting system but you want to store the products in each warehouse and sell separately, in this case you can have various sales-teams for each company and have various warehouses for each one too. you can also have separate point of sale for each team.

other way is Creating a new warehouse in  inventory.

In order to be able to create a new warehouse, you must allow the system to manage multiple locations. In the Inventory module, open the menu "Settings ‣ Configuration". In the Location & Warehouse section, tick the Manage several locations per warehouse box, then click on apply.

After that create new warehouse according your requirements.

this way you can manage different branch of your company.