I would say that you can do this by by simply managing the minutes as I say.
So looking at situation I would assume that you have studied your 12th wisely.
- In this interval you need to cover the electrostatics and capacitor only revision is needed then go for some concept related questions.(follow the same with current, magnetism, optics and machnics and then start solving the questions from any mains level book i would recommend the arihant one
- From chemistry start with inorganic and i would recommend bonding in atoms. Then again follow the same with organic and physical respectively this will make you clear with the concepts
- maths should be started from quadratic and complex no. then 2 and 3 dimensional Geometry(maths is all about practice. solving 30 questions from each topic wise chapter kownly calculus, vector, and coordinate.)
Try to complete this 15–20 days and start solving 5 sample paper and questions you are not able to solve practice and revise them from ncert. would help you complete your syllabus thoroughly. and again solve 2 to 4 sample papers. best of luck