You've got excellent advice from others here. I agree that your experience is quite normal, as are your feelings. It's also common for new or junior students to feel they are detracting from senior students' experience and practice. It's also not unheard of for senior students to feel they are being held back, or feel bored, when they work with junior students. As for me, I'd been studying Taekwondo for then 30 years when I walked into my first Aikido class. Boy did I feel like a schlimazel. And it took several months of it for me to get comfortable enough to keep coming back to class, despite my other experience.
So there you have it: you're normal, and your peers are normal.
As to your peers and their feelings (the one who went off and did his own thing), that is a childish attitude. All senior students should be taught that at some point in their martial arts journey, they will have to work with junior students. That is a time for reflection and patience, and to focus on the basics. My senior students may occasionally feel frustrated, but they would never display such arrogant behavior. I've only once in my life seen a student shown the door, and told never to come back again, for that kind of behavior. Most of my students, and students in schools where I am a student, and myself, welcome the occasional opportunity to work with a new student. Not only does it bring about an opportunity to make a friend, but it helps keep a student in the school, which makes the school stronger, and longer lasting. Everyone has an interest in taking new and inexperienced students under their wing from time to time. My advice to you, when you come across such arrogant students, is to ignore them.
As to the student who helped you, that is to be expected by an instructor, so you shouldn't feel bad. Her helping you re-enforced what she was taught, and so, by helping, she learned. I don't think it was wise to have a student 10 minutes into their MA journey to be learning break falls in a general class, that showed some inexperience on the instructor's part. But it happens, so, expect to feel awkward.
There's an old cliche - sorry, but it's relevant - that a black belt is nothing more than a white belt who didn't quit. Do you think that even the best martial artists today - the actors, like Steven Segal, Chuck Norris, Jackie Chan; or your instructor or senior students; or the founders of all the styles in the world - started out as advanced and capable students? No, of course not. They ALL made their mistakes. And all (except one of them, we'll just not mention his name) will fully admit they have a lot of learning to go through, and make mistakes even now. And this is true for any art: plumbing, electrician, computer programming, painting, glass making, smithing, sports... All start as novices.
So take heart: you're a normal student. Expect to make mistakes, that's primarily where you learn. They answer all of the "why" questions you might have:
Instructor: "Do it this way"
You: "X!#&*@#" ←------ learning!!!
Instructor: "That's why"
By the way, in the next few months, where ever you end up at, you'll meet another new student. You will probably feel quite empathetic toward that student, as you will understand how they feel. Don't be that jerk who walked away and did his own thing. The first skill you help that student with, you will feel like you learned something, something that clod will never know.
Finally, I will also say this: Don't pay much attention to the other students in class. That is, don't compare yourself to them. In any given technique, there are a myriad things that have to be done to accomplish it. You are working on one of those myriad things, and they are working on something else in that myriad of things. Focus on what your instructor or partner tells you to work on. If the construction workers focused on the window treatments instead of the foundation they were supposed to be pouring, then the foundation shouldn't be trusted. So you should only focus on what your instructor tells you to focus on, and don't worry about the rest. When you do one thing right, you'll get to correct something else later. Don't try to correct everything, or nothing will get done. Always go home with the expectation of doing at least one thing right, not everything right.