Multitasking doesn't increase productivity:

It can take 20-40 percent more time to finish a list of jobs when you multitask, compared with completing the same list of tasks in sequence. 

Forget about multitasking and, instead, focus on one task at a time. That way, you'll produce higher quality work.

Doing more than one task at once is completely anti-productivity. It is nearly impossible to concentrate on two tasks at the same time. This way of working is inefficient for focus and deep work. If you are doing shallow work like washing the dishes, multitasking works.

Multitasking has been proven to reduce our cognitive abillities due to the fact that the brain can only fully focus on one task at a time. Even though multitasking can be beneficial in various situations, you should avoid it as much as you can whenever you deal with important tasks.