Double N-Back is a game that may improve your working memory and mental sharpness. It trains the player to hold information in his mind and work with it to solve problems.
Double N-Back based task:
There are double n-back applications for your mobile phone or computer. Here is one: https://cognitivefun.net/test/5
Simply download one and play. The rules will be explained to you in the application.
2 times per day
Morning and afternoon
It can cause some stress at first because it can be difficult.
Memory Dual N-Back - Amazon