Updated review 15 04 2023. Having realised the cost of booking through Ninja is a mark up of nearly 100 percent for a service that only costs 1.5 euros in the UK, I will be more careful in the future.
I have to say that the booking process was easy and similar to other ticket providers. I have two comments to make. First the tickets were issued in Portuguese, a language I am not familiar with. I am surprised that there is no second language on the ticket. Secondly I have been issued seats 22 and 28. It seems that the two seats are not next to each other but we have no way of checking.