>>13032893High quality and 7-9 hours of sleep; enough vitamins, minerals, protein and calories from food (try canada food guide, it's quite nice (albeit, not the most precise) for starting your health journey); and enough physical exercise will ensure that your cognitive functions are in good shape.
Planning is quite easy: you start with the most urgent task that can be finished before deadline, then go to another most urgent task that can be finished before deadline. Include recreational activity in your plans (best with friends or family if possible). Don't work more than 9 hours per day, working more than that just becomes inefficient.
Multitasking requires you being very proficient in all of the involved tasks (or pen and paper to keep track of every task and being able to return to them). Easiest example here is cooking: usually people can't cook two fairly new (to them) dishes at the same time. With enough practice they can.
Creativity is usually about knowing something good enough that you know multiple ways of doing it and then implementing the the way you like or need or whatever; or about trying different approaches or methods when doing something and watching results.
If you want to learn to do something quicker, do that thing a LOT of times. Eventually, it will require close to zero mental effort to do it, which also will decrease amount of time lost on thinking or doubts or mistakes.
