What is the most efficient way to study IB HL Math, Phy, and Chem?

[EEjae]

Hello,

I am a Pre-IB student, going into IB course this year and I have few argent questions that I desperately need to know. Here is why. As a middle school students, our school took on IGCSE course and during IGCSE, I was quite confident on my science and math score. So after IGCSE course has finished, I chose HL Math, HL Physics, and HL Chemistry for my HL subject for IB. After I finished choosing and submitting my subject choices, I asked the previous year students about how IB was. When they heard about my subject choices, they said I am totally doom since the subjects are crazy hard. I am kind of in panic now. I am worried about all the work I will have to go through in IB. Also, I am interested in playing guitar, composing, and coding stuff. I am wondering I should give up on these hobbies if I want to pass IB. To be honest, I want to have enough time for me to do these hobbies during IB, while getting good grades on IB subjects.  In order to do that, I am planning on finishing all the work and studying in the most efficient and time saving way as possible. Fortunately, I have about 2 month during summer break to prepare for IB, and I am looking for things I should do during that time which would save studying times in the future. Please reply if you know efficient way to study IB HL Math, Phy, and Chem or have any advices for me. Thank you for your helps!