Greetings to you,

For the upcoming JEE in the month of January 2020, I would suggest you to stick to basic concepts thoroughly. If the basic concepts ate thorough, you can solve any sortof intermediate and advanced problems. For chemistry, you need to get done with NCERT atleast 3-4 times to score well in the organic and inorganic chemistry setion. For mathematics, keep practicing through coaching material and do take help of refrence books but make sure to not go deep to the advanced syllabus. For physics, HC Verma itself is a sufficient for JEE Mains. Also you can take up DC Pandey for practice in Physics. Make sure to solve maximum number of question papers from past years with a three-hour time limit. The quality of questions are far important than the quantity of the questions. Make sure to solve those questions that covers 2-3 concepts at a time. Good luck.