Normally, practising more questions allows you to complete subsequent questions faster because cognitively, ideas and thoughts come to mind faster as you become more familiar with the content and more used to the way of completing questions.
Alternatively, a method I've used to finish exams on time that does not involve doing questions faster is by completing questions where the solution comes to mind quickly, and leaving the more complicated ones (the ones that take more time and thinking to complete) till you have completed the easier/shorter questions, leaving you with more time to work on the questions which you're struggling to finish in a timely manner and this should help you finish your exams on time.