The location is perfect. The host Caroline is great!
You are about a 20 minute walk from several busy shopping streets, with great restaurants and Gaudi architecture. I would not want not want to be any closer. The apartment is on the 6th floor (really the 8th), so you have the top apartment with two balconies. And yes, there is an elevator. Access to the apartment is handled via an App on your iPhone. It was a little tricky, but nothing you can't figure out in a minute. You need bluetooth and wifi on your phone (and maybe cell service) for it to work.
Each city block has grocery stores, and this apartment was no exception. There were 4-5 stores within 3-5 minute walk. The apartment has a kitchen where you can do a little bit of cooking and prior guests leave spices or olive oils. There is a Nespresso machine in the apartment. You can buy pods at any store in Barcelona.
The balcony is amazing. The views are great. You can see La Sagrada Familia from the front and back balconies. The July sun was hot, but the large balcony is great for morning coffee.
The space is large for two people and can fit a family of 4 very easily with space to lounge.
We had a long stay and Caroline was very accommodating by getting us extra towels and sheets. If you need there is a laundromat literally across the street. Interestingly, there is a laundromat about 5 minute walk away where you can have coffee, wine or beer while you wait.
The cross ventilation is great and the air conditioning in the hot summer is nice and cold.
I would definitely come back here rather than a hotel.