What would someone do during a couple of days before jee main 2019 that he/she know formulas and conc. in an unclear and not in concise way?

If there is only couple of days left with JEE main then you should focus on the formulas which you could not remember easily therefore prepare a list of the important formulas which are important from the point of view of JEE main but you find it difficult to remember don't go for all the formulas because it will create a long list and you will not find which one to remember and which you are already remember therefore just english dose formulas which are difficult to remember and are very important for JEE main and try to look at those formulas time and again and solve questions based on them to remember those concepts and formula easily.