Benfica Tickets

[Jamesbenfica2018]

Hello Benfica fans. I am travelling to Lisbon for a city break in March and would love to go to a game. I know Benfica are playing Vitoria that weekend. How can I get tickets? I have tried on the Benfica website and they don't seem to sell any for that game.  Also would it be easy to get tickets or do they always sell out?

Thanks.