You're already spending a good amount of time on studies, perhaps you might even want to cut down on it a little bit (depending on what you're studying for and when the exams are). Make sure that you're taking adequate breaks in between.
Use the pomodoro technique while studying (25 minutes of focus followed by a 5 minute break). After 2 hours of studying, take a longer break.
To score good marks, the simplest thing to do would be to start answering question papers. Do you have a set of previous years' question papers for this exam? Simulate an exam environment. Set a timer for the required duration and answer those questions.
Practise answering questions daily. Compare your answers with the correct ones. Find out where the gaps are and focus more on those areas.
Other than answering questions well with the specific intent of scoring marks, there are also learning techniques you can implement to deepen your understanding and retention of information. Please check this thread where we have explained this in detail.