To be honest with you and no disrespect, unless you put atleast 18 hours of concentrated preparation, you cannot achieve 180 out of 200. As of now it is  not clear as to when might the exams be held. Even if they are held in June, you need a solid strategy for preparing for UPSEE. You should strictly follow a time table. practise as many sample papers as you can, attempt atleast one mock test a week. Yo should also memorise the periodic table and all formulae so as to be good with these 2 subjects. You need to revise the entire syllabus atleast thrice so as to be able to remember what you studied and convert it into answers on the D-day.