There are a lot of mixed opinions on Duolingo. However, I can personally confirm that Duolingo is great to learn Spanish vocabulary, practice building real-life sentences and practising verb conjugations.
A lot of Spanish learners stop within the first few months. Why? Because learning any language is extremely difficult and you won’t be fluent in a week, a month, 3 months or even a year.
Duolingo, nor Learnish will make you fluent in Spanish, or any language. That is something you need to do yourself, by practising, being motivated and putting the time and effort in whenever you can.
To learn more vocabulary and learn how to talk about real life topics, I highly recommend using Duolingo, but please take the above information into account when learning.