wasting 3 to 4 mins in unsolvable qst in quants but I know the concept I know how to start the qst when I read the qst, but getting struck without getting the answer. so potentially wasting around 15 mins and getting only 5 qst right. what strategy should I follow in quants?

Practice

follow round system, in round 1 do only those which you can formulate a solution while reading and those which you have done before. And leave those which you think you can try and succeed for round 2. Also, maintain clean rough work, it will be useful for round 2/3 and mock analysis also.