Here is the deal with multi-tasking. Some people will say that multi-tasking is really a myth. What you are really doing is just jumping from one work thread to another in rapid succession. Effectively you are like a processor, sure you can have multiple threads in queue, but you can only really process one thing at a time. The question of how efficient you can be really comes down to how many errors you commit.
If you do only one thing at a time, in serial fashion you will produce less errors. In fact, you could get to a point where you make no errors if the task you are completing is the same all the time. This is really efficient, but if you have a lot of tasks to accomplish, not very practical. The temptation therefore occurs where you want to work on multiple streams at once. Multi-task. You can work on things in parallel. This will help you become faster, if and only if, your error rate does not cause you to repeat things to much and end up going back and redoing work.
So yes you can multi-task and you can be fast, but only if you are not producing so many errors that you end up going slower than you would have if you just did things in complete serial fashion. So what is it for you?