Your 150 days weren't wasted, but you're frustrated about exactly the right thing: Duolingo teaches you some vocabulary and sentence structures, but that's really just one side of the coin. The other answers are right that the app alone isn't enough - but that's not because Duolingo is bad, it's just because it's only a tiny part of language learning. It's like if you only trained your biceps at the gym and then wondered why your legs are weak. 🏋️
For real conversations you need input from real people, ideally with real voices and different accents. Podcasts in Spanish, YouTube videos, maybe even some movies or series - that should be running in parallel. Even more important: speaking practice. Sign up for platforms where you can chat with native speakers or do quick calls (there are several free options out there). The combination of "passively listening and reading" plus "actively speaking" makes the difference.
Don't give up on Duolingo because the routine is genuinely valuable - but see it as a supplement, not the main meal. If you combine the app with actually consuming Spanish-language content and start speaking (even if it's embarrassing 😅), then you'll crack the problem. Three months isn't that long anyway, your brain just needs more material to work with.