Good am guys!!! 
I just wanna ask how to create a menu using arduino nano and connected to I2C lcd display with dht11 sensor and keypad. In the program i would like to create a menu wherein i can change the current reading of the dht11 sensor
when i press [D] Menu
"Set Temperature"
when selected "Set Temperature"
i will input the desired temperature i want, then the current temperature will change to what tempearature i input.
It is surprisingly complex to do this. In the Arduino there's no helpers. No built-in "menu" class or anything. You have to do all the work yourself: writing to the screen, repainting the screen after the menu goes away, debouncing buttons and all the rest.
As in all good learning environments, completing the task is left as an exercise for you to do on your own. I suggest starting with reading tutorials related to the specific screen you have.
However, there exist a few menu libraries for Arduino. I don't know which is the best, maybe you should try the most recent one. But as was said before, you'll have to do most of the work to adapt it to your own needs.