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The Feynman technique, active learning, summarizing key points, traffic light method, Parkinson's law, practice past exams/quizzes, Pomodoro technique...
You can improve your focus and concentration by breaking down study sessions into shorter intervals followed by short breaks, and try as much as you can to minimize distraction, a quiet space would be also helpful turning off your phone could be one.
You can set up very strict deadlines in your calendar to create a sense of urgency and practice self-discipline and time management.
You can practice stress management exercises/techniques such as deep breathing, you can always seek support from your close ones.
Resources that you can use: textbooks, online lectures, flashcards, study groups, youtube videos, educational applications or software.