Transportation Bratislava

What type of transportation would you suggest me and my girlfriend for 5 days in Bratislava? We mainly just want to walk inside the city but would love to go outside the city for example in the north or Hrad devin. Would you just use single bus tickets for that, do I buy them in the bus via card? Or is there like a day/multiple day ticket that include the outskirts of Bratislava?