This isn't tremendously difficult on the whole, but it can be a little tricky.
Some hints:
4) In area 1-4, be aware that you need to avoid waiting for lasers as much as possible. In particular, in the second room of the area (the room that you think you're clever for waiting for one sweep of the lasers to cross across the middle), in reality you must move across immediately, use the barrier on the far side of the room to skip the right-facing laser and move ahead of it, then rush to the teleporter. This is necessary so that you can immediately rush through the third area without having to wait for those lasers to pass by.
It is absolutely necessary to do this to get the target time.