Stuff like Duolingo is good for building a foundation of vocabulary, but if you want to get ranting you have to immerse yourself. Movies, podcasts, audiobooks (reading along with the physical book so you can practice both reading and hearing at the same time is also great), whatever else you can think of where people are speaking fluently. You won't be able to understand at first, but used in conjunction with those apps that teach you individual words, your brain will eventually start to catch up. Sometimes I even read aloud to myself to practice speaking. But vocab apps alone will never have you reaching fluency.

Watching kids shows in a foreign language is also very effective. They're often literally designed around conveying messages to people with a tenuous grasp of the language :)