You can start reading here about inventory:
There are also other guides on the forum about it.
There isn’t specific support for doing a PO, however when you do your inventory purchase, you essentially are creating a document in the system that could be considered as your PO.
If there is a specific way you want it setup, with SambaPOS you can built the feature. So the answer is not so straightforward as a “yes” but I would say it is possible to add the functionality based on your requirements as SambaPOS is very flexible. The difference between SambaPOS and pretty much all other POS software is that with SambaPOS you can build your own functionality and customisations to make the POS software work the way you want to, rather than you having to change your business logic to work around the POS software. It’s a different way of thinking but it means you can grow the solution as your needs change.
Hope that helps 