Hello there,
Do not panic about your examination. If you prepare well, you can definitely get good results. Here are some suggestions that you may follow:

1. Make a timetable covering all your subjects and follow them. Try to keep few days in hand for revision.

2. If you cannot study for longer periods at a stretch, take small breaks in between. But try to complete the chapter within a day. Once you complete a chapter, go for the practice questions.

3. After completing all the chapters, go for the previous year question papers of both your school and your board. This will give you an idea of the trending questions.

4. Lastly, eat healthy and sleep well. Stay calm.

Try to follow this routine, you will get good results.
Hope this helps you.
Good luck!!