I took Spanish in high school and college, so had a rudimentary understanding of verb tenses and some vocabulary. Before I walked the Camino de Santiago el Norte (45+ days in Spain), I used Duolingo to brush up on my Spanish.
It helped my reading most, my speaking a fair amount and my listening/conversation the least. I was able to ask questions, but was often flummoxed at any reply that wasn't the most basic.
I grew to hate the gamification, but was addicted to my "streak' also ... using math lessons when I didn't feel like doing a Spanish lesson. The so-called "leagues" were kind of useless since the same people weren't in the league from week to week. Any friendly competitiveness to "learn more" was lost when randomly assigned to a different group each week.
I finally abandoned the app this spring.
I'm trying Babbel now since I'm going back to Spain for a month and Patagonia next year.