Hello Aryan

Yes you can definitely score 600 marks or more in your beet 2021 examination, you have more than 1 complete year.

You should not waste time and stress just because you are not able to perform well in your tests now, first of all go through ncert to clear your basic concepts and have a good grip over it and you can take the help of reference book to understand the topics you find difficult to understand, Ncert is really good for clearing your basic concepts especially for biology, you can follow books like Trueman's biology as well for reference and follow books like hc verma for physics and op Tandon for chemistry, after finishing each chapter you should practice numericals and mcqs and keep revising your concepts whenever you feel like you are for getting some concepts .

You can make a routine as well and try to give at least 8 hours or more to study , your routine should revolve around studying concepts and practicing it by solving mcqs and numericals.  You should make a list of important formulas in chemistry and physics and important diagrams in biology etc. and you can brush them up weekly

You should practise numericals and mcqs , go through past 39 year chapterwise papers of neet aipmt book for each of Physics, Chemistry and Biology by arihant and once you are done with the complete neet syllabus go through mock test papers. Just be positive and prepare well and you will be able to score 600 or more

I hope that it helps you

Thankyou