You should just solve as many papers as you can within the prescribed time limit of 3 hrs. That would help you build your speed. Since you could not clear jee main, you should also focus on the weaker areas. I would also suggest a complete reading of the NCERT textbooks. Solve the prev years bitsat papers that are available on this website. Solving the papers that only have theoretical questions might be a waste of time. Try finding some more trustworthy sources whose papers resemble the actual paper pattern.