Hi doctor, i don't know whats wrong with me i cannot learn stuffs. i read books i can comprehend stuffs but i cannot keep the information in my head. and sometimes it's quite hard to read because my mind nah i know these stuffs but actually i don't?

Would wonder about a learning disorder such as dyslexia. You could see a speech therapist or a psychologist, or both, and evaluation(s) may well reveal specifics. This could lead to effective therapies.

If one is 24 years old, the assumption is that one has gone to high school and possibly college. The first question is when did this "i cannot learn stuffs" begin - recently/long time? Any major trauma -physical/mental/emotional... Difficulty concentrating could also indicate Major Stressors in one's life/environment. A qualitative talk with the PCP/Neurologist/Psychologist is indicated...