This is probably all normal!
Motivation/passion comes and goes - that’s okay. Just commit to doing five minutes per day (maybe take one day off a week). You might find that after five minutes, you don’t want to stop! I would say - don’t get stuck on CSS and it’s tricky for most people - try not to beat yourself up over it. I think it’s okay to move on to something else and then come back to it later - it might even be better in terms of long-term memory formation. Things might even make more sense with a bit of diffuse thinking away from directly focusing on the problem. Find multiple resources - like Udemy courses or other - things might look brighter with the help of different approaches. Read the posts about people getting jobs.
It might be tempting to just keep working “harder” when you’re exhausted, but mental energy is finite - Definitely take breaks - every 50 minutes, take at least a 10 min break. Prevent burnout - it’s difficult to recover from. And spend no more than 4-5 hours learning difficult things (that’s about all humans have mental energy for). Find some time each week to completely disconnect from the problem. Find other hobbies that fill you up and revitalize you (maybe your life doesn’t have to be repetitive?) - take care of yourself every day. Someone once told me - “Spend energy to get energy.” So, watching Netflix is one form of taking a break, but it won’t necessarily energize you (unless it is some inspirational autobiographical piece).
Learning should actually be a little hard. If it were easy, everyone would be experts at this stuff. I highly recommend reading some motivational material like: “Talent is Overrated” by Geoff Colvin, Carol Dweck’s “Mindset”, and this course: https://www.coursera.org/learn/learning-how-to-learn
And I think it is awesome that you are taking on this project when you’re only in high school! Keep learning!