Good news! You're already living the quickest and most effective way of learning Chinese every day. You're in China, immersed in the language, and making an effort to learn. Immersion is an essential part of learning, and what many don't realize is that simply being present isn't immersion. You have to make the effort in places like China because it's so easy to simply fall back on English. You're making the effort. Good work!
So what more should you be doing?
1. Get a teacher: You're a teacher yourself, so I'm sure you recognize how valuable having a teacher actually is. I won't go into detail on this point, but imagine your students trying to learn a language on their own. Chinese is difficult for most people in the beginning, and while it's admirable that you're making an effort to learn, the wisest choice would be to invest in proper lessons with a qualified native speaker.
2. Study a lot: Hitting the books isn't the most attractive solution, but it is a key part of the solution to your problem. I tell my students that they should be spending at least two to three hours on their Chinese studies every day. That doesn't include speaking drills. How much time you spend on speaking drills is up to you, but make sure you do them. A great way to feel encouraged is to be able to speak to people and have them understand you. Don't neglect speaking! When you're not doing formal studying, try to integrate what you've learned into your everyday activities. Interpret signs, string sentences together in your mind, and communicate with people as much as possible. Make a few Chinese friends.
3. Write: You can file this under studying, too. If you want to memorize characters you need to write them. Flashcards are great for when you're on the go, but strengthening your good old muscle memory is just as important. I suggest buying special notebooks with grids inside for practicing characters. You can get them online, or you can visit a bookstore. I suggest a bookstore near a university with lots of international students.
4. Travel: This might not be one of the answers you expected, but trust me, it helps. Not only is travel a great way to see more of China, it's also a great way to experience the many different varieties of the language. Tying what you've learned back to memories of new experiences is an excellent way to make sure you don't forget things easily. Plus, travel is fun, and there's plenty to see in China.