I do not know Barcelona at all: if you can get over the horror of a guided tour, take one. I always do in a new city:
https://www.tripadvisor.com/AttractionProductDetail?product=3142BARCELONA1&d=190166&aidSuffix=xsell&partner=Viator
Do it the first day and you'd be surprised how informative they can be. I don't mind looking goofy for a few hours learning about the city.
This one looks great:
https://www.tripadvisor.com/AttractionProductDetail?product=14218P6&d=191040&aidSuffix=xsell&partner=Viator
On a different tack, a friend of mine swears these type of classes are great anywhere:
https://www.tripadvisor.com/AttractionProductDetail?product=16637P1&d=3757398&aidSuffix=xsell&partner=Viator
He lived in Italy for four years and took cooking classes in a number of cities. He and his family had a ball.