Many things to say here.
1. Assuming by the reported strong growth currently, you are in the northern hemisphere. You can add your general location/region/country to your profile so that you will get the best advice for your climate.
2. Bonsai are not houseplants, so they will survive and usually thrive outside, whereas trying to grow them indoors usually results in their death (your photo is taken in a bright and sunny indoor area, where outdoor conditions are much better for a tree).
3. Rely on the experience available here. In most threads discussing this, there are several things to do before your tree begins its bonsai journey. First rule of bonsai (maybe?) is to start with a healthy tree. Once you figure out how to keep your trees alive and vigorous, then you will be ready to move on to the more advanced steps, and then the next. And the next.
4. Don't just take my word for it; I'm a beginner, too. I'm repeating what I've learned, both from reading and from doing.
Welcome to the NutHouse! Get ready for a science-meets-art joyride!