This app was mentioned in 2 comments, with an average of 1.00 upvote
I haven't used OmniFocus, but I have found a GTD app on Android that I'm happy with and would certainly be a big improvement over Google Keep. Chaos Control explicitly supports projects and contexts as well as stuff like recurring tasks and task start/end dates. Another plus: Chaos Control is free, but Premium only costs $5 and will get you access to the webapp so you can use it from anywhere. I have encountered a bug or two, since it looks like it's maintained by a single developer, but support has been extremely responsive. All in all, it's by far the best GTD app I've found for Android, and it's ridiculously cheap considering apps like Any.do want to charge you $50 per year. It'll certainly save you a lot of time, money, and effort if it keeps you from having to buy hundreds of dollars worth of hardware and split your platforms between Android and iOS.
Edit: Link for basic