Barcelona is an easily-walkable city, and most of the suggested locations above are within walking distance. Of course, there are still options for taking public transit if you prefer. The most cost-effective way of getting around is purchasing the T10 pass, which allows ten trips on buses and metro lines for €10.20. Taxis in Barcelona are metered, with typical rates of €1.10 per km, and Uber is also available throughout the city.
If you have additional time, consider visiting Park Guell again, attending a live flamenco show, or viewing the works of the celebrated artist Joan Miro at the Joan Miro Museum. Alternatively, if you have less time, consider combining Day 5 and 6 or eliminate the day trip to Montserrat. Lastly, make sure to plan your visit in good weather (April-June, September-November) to make the most out of your trip to Barcelona.