This app was mentioned in 7 comments, with an average of 1.71 upvotes
Are you in the U.S. or Canada? Because if so, I'd highly recommend Mango Languages (free through many libraries); they've wonderful grammar as well as usage and cultural notes built into their courses.
Although I know nothing about trackers, a possibly better app to learn languages would be Mango, it's free if you have a library card but also has a lot of languages to try out!
Good luck on your language learning journey!
Hm. iOS has some great language learning things, but they sadly aren't on Android.
You may be able to get Mango Languages or Rocket Languages for free, if any of your nearby libraries is a participant: https://play.google.com/store/apps/details?id=com.mango.android or https://play.google.com/store/apps/details?id=com.rocketlanguages.app
They start out simple, but I'm pretty sure they both get relatively advanced in later lessons.
LingLing is a silly, but kinda fun, vocabulary game: https://play.google.com/store/apps/details?id=com.hepilabs.lingling.spanish
I also thought this was kinda fun (although maybe a bit limited if you've already finished DuoLingo): https://play.google.com/store/apps/details?id=com.nativetongue.spanishsmash.game Full version is $3: https://play.google.com/store/apps/details?id=com.nativetongue.spanishsmash.pro
I really like Mango! https://play.google.com/store/apps/details?id=com.mango.android&hl=en