I want to qualify jee mains with good marks so what can I do now to prepare for it

In order to get good marks in JEE Main your base should be strong. You can take help of NCERT books to make your concepts strong. It is recommended to solve exercises which are given at the end of the topics in NCERT. You can also get direct questions from NCERT.

Apart, from NCERT you can refer below books

Physics
HC Verma
DC Pandey

Chemistry
Organic Chemistry- Morrison Boyd/O.P Tandon
Modern Approach to Chemical Calculations- R.C. Mukherjee
Numerical Chemistry- P. Bahadur
Concise Inorganic Chemistry- J.D. Lee

Mathematics
R.D. Sharma
M.L. Khanna

You should focus on important topics and try to complete then first as they carry maximum weightage. You can check the topics below

Mathematics-

Coordinate Geometry
Continuity/ Differentiability, Limits
Complex No., Quadratic equation
Integral Calculus
Sequence and Series
Trigonometry

Physics-

Current Electricity
Electrostatics
Optics
Heat and Thermodynamics
Law of Motion
Waves
Simple Harmonic Motion

Chemistry-

Transition Element and Coordination Chemistry
Periodic Table and Representative Elements
Gaseous State
Atomic structure
Amines
Solution and Colligative Properties
General Organic Chemistry
Carboxylic Acids and Derivatives
Hydrocarbons
Carbohydrate, Amino Acids and Polymer

You should refer previous year papers as well to understand the exam pattern and level of questions. Solve as many as mock test series to to analyze your preparation level at regular period of time.

All the Best!!