You can easily fill five full days in Barcelona If you want. I’ve spent about six weeks there myself off and on this past year
El Nacional is a great recommendation, I’ve been there before and I only had a couple of cocktails but the food at the various restaurants looked and smelled great.
For tapas in Eixample one place I wouldn’t miss is Cerveseria Catalana. Just excellent tapas there, I’ve been there multiple times. It’s a great date spot as well.
Another cool spot nearby in the Gracia neighborhood is Plaza Del Sol. It’s surrounded by restaurants and bars with patios and lots of young people hang out there in the evenings.
I’m sure you know this, but dinner in Spain is typically from 8 at the earliest until 11. 9 pm is prime time for dinner. Unless y’all wanna eat alone don’t go out for dinner at six or seven.
I wasn’t too big on the cocktails myself while I was there, usually I was either drinking wine / cava or Estrella on draft.