Controller input issues

I recently bought a Bluetooth controller from PowerLead for use with the mobile edition of Minecraft:Bedrock.

I played in the game for a while with the controller connected and noticed that Minecraft receives the input of the controller in a strange way.

For instance, pushing 'up' on the left joystick results in my character looking up, walking forward, and sneaking at the same time.

I thought it must've been an issue with my settings, so I went there and tried to set the controller inputs. But whenever I try to put in a new button, Minecraft still recognises the input from the controller as it is and moves the menu screen. (Example: attempting to set the left joystick to move forward results in the entire menu moving (and thus exiting button assignment mode) and not letting me set an input.)