I have a poor memory. Please tell me a dua from the Qu'ran and Sunnah with which i can improve my memory

First and foremost, abstain from sin. Sinning adversely affects the memory.

You may try the following: Immediately after the performance of Fardh Salaat, place your palm on the forehead and recite eleven times ‘Yaa Qawiyyu’.

and Allah Ta'ala Knows Best

Mufti Muhammad Kadwa
FATWA DEPT.