Single Task not Multitask
Multitasking doesn't exist. People who think they are good at multitasking usually aren't. The brain switches context rapidly, focusing on single tasks before switching to another.
A better way to work is to single task. When you work on something, focus only on that. Maybe set a timer.
It's not to say you can't have multiple projects, but rather when it comes time to sit down and work you focus only on one task at a time.