Since you are appearing in the upcoming june session, therefore, you have plenty of time for the preparation. I suggest that first complete the syllabus and then start doing past papers.Past papers are really important so practice atleast 5-7 years (or even more if you have time) and that will really add to your preparation.
Physics and Chemistry are not much difficult subjects, you need to have basic ideas and strong concepts for all topics, if you’ll have that, i think you can definitely ace them with good grades.