My supervisors take long time to respond to me
There isn't a lot you can do on your own. The supervisors have their habits. The best advice I can give is to try to find someone to speak to them on your behalf to get them to help you meet the deadlines. You want an advocate that will be respected by the supervisors. Deans are good for this sort of thing, actually. 

But if you can meet face to face with people, either the supervisors or an advocate to help impress on them the urgency it would be better than trying to do things by email, which is asynchronous by design.