Everybody learns differently, not just from perspective of being a more visual versus auditory learner, but also how long it takes to pick up concepts and be capable of employing those concepts into real tasks.
You could think about what amount of time a University course is over the space of an entire semester, which is normally about 35-40 hours in total; and does that amount of time in a 101 course provide somebody with everything they need to go out there and do things on their own? It might allow them to continue their learning and do some of the at home projects, but likely not getting a job in the field.
With 6 hours a day, you’ll need 7 days to get to 42 hours…but that is not even enough time to build a real app, even for the most experienced experts in the field, so definitely not enough time to learn everything you need to know to build a complete app.
Then of course, there is the time it takes to stumble and really hit a brick wall with a feature of the app you are trying to build, which for me personally, has at times set me back 20-30 hours worth of searching the internet and playing around within Bubble itself to attempt feature and finally get the feature functioning properly.
If you are asking, how much time to learn the basics of Bubble to be able to piece together a MVP, likely 2 months working 6 hours a day, and in that time you might have completed the MVP. If you are asking how long to learn Bubble to build a real app, likely 6 months working 6 hours a day, and at the end of the 6 months you will be itching to go back to the features you build in the first 1-3 months and rebuild them to fit your greater understanding of Bubble you acquired over the 6 months. And if you are asking how long to learn Bubble to become an “expert”, likely 2 years working 6 hours a day, and keeping in mind that to be an expert in a field, it takes continuous efforts to be a life-long learner of the subject, plus knowing the new features that become available as Bubble releases them.
The understanding I have of Bubble and my abilities to utilize that knowledge into projects has increased drastically as time has gone on. I started when there were not the variety of learning resources and materials available as there are now, so my learning curve was much steeper compared to the learning curve new users would experience today. When I first got started, I didn’t feel competent enough to charge people for my development services until I had been using Bubble full time for about 18 months. I did however, get competent after about 6 months to feel as if I knew enough about Bubble that I could build most anything I would want. If I were to compare what I could do after 2 years on Bubble versus 4 years on Bubble, my 4 year experience self looked at the 2 year experienced self as a novice.