What is the problem?
- you cannot create two joysticks
Here is an example showing how to make a 'joystick' with Buttons in a game Mountain Kingdom - a chat real time two player, two device game using the CloudDB and a Canvas. You could use two Button joysticks. - you need to interface the joysticks to the arduino
- something else.
What have you tried Enzo?
Essentially, you are trying to control a robot. Here are community discussions about controlling a robot https://community.appinventor.mit.edu/search?q=control%20robot using an arduino. They may help.