What is the fastest and best way to improve my memory, cognitive skills and span of concentration?

Simply use your brain instead of machine such as mobile apps. Use the magical number to short list your stuff. Magical number is 7 + or - 2, which means minimum amount of things to remember is 5 and maximum number is 9

Wake up at the same time every day, preferably in the morning. Eat a good, relatively large breakfast, daily, avoiding excessive carbohydrates and sugar, soon after waking.It is very important to establish temporal routines of this sort, as it is very difficult for your body to develop and maintain any emotional stability and capacity for sustained effort if your basic biological rhythms are continually upset. It is also very important not to subject yourself to stress without eating, when you start your day, because you can't recover from that until you sleep again.Developing these two habits will help you more than anything else you can do. Furthermore, you will not ever be able to perform optimally unless you do so.

the fastest and best way to improve my memory is that Try to love and give attention for the incident which we wants to remember, and cognitive skills and span of concentration, , if we cant do like that just try to watch those things for some moments continuously,

when we are trying to look continuously in to one thing automatically we can remember and can improve the concentration also; if we wants to improve our cognitive skills we can do some other things like try to say our self that I am going to do this thing and think about it for a time.....