implement e-invoice into odoo 12 CE

Our Government demands that we establish a gateway with them for electronic invoices. We are in a small country (Cape Verde) and I could not find any information on how to do this. We are looking for someone who can do this or teach me how to implement e-invoice from scratch, i.e I have no clue how to start this task.

All the documentation is in Portuguese but I can provide translations if needed.