If you believe what others tell you, i.e. "too old, can't study, etc." then that's exactly how you will be. There's no such thing as "brain does not work." You have a very negative opinion of yourself, and until you change that and tell yourself you can succeed, there's really nothing much others can do or say to help you.
Also, it doesn't matter whether you prefer to study alone. If it's not working, it's time to do something else. Talk to other students in your class, especially those who are doing well. Ask for help. Talk to your instructor. If you're having trouble with English, then how can you expect to be able to work as an LPN or to communicate with your coworkers and patients in the future? If English is the problem, then take an English class first. If it's not, then work with your classmates and help each other to study.
For me personally, reading my textbook prior to the lesson helped me pick up concepts faster than sitting in class trying to understand things for the first time.