Your 3-speed Citizen Bike includes a Shimano Nexus internal hub.
Though your hub system is relatively maintenance free, this system requires regular inspection to ensure proper shifting. If your shifting requires adjustment or is not operating properly, please check for the proper adjustment.
To adjust the hub, first set your grip shifter to second gear.
Next, remove the protective cover to expose the hub pulley by removing the retaining screw and cover.
Note that the hub pulley has a red indicator line that may or not be visible in the 2nd gear position.
For a properly adjusted hub, this red indicator line will be evenly aligned with the threaded axle end.
Shift your grip shifter between gears to note the travel of the pulley and to reveal the position of the red indicator line if needed. Return the grip shifter to 2nd gear.
To adjust the position of the red indicator line, you will need to adjust the gear cable tension by rotating the barrel adjuster until proper alignment is achieved.
You may need to release the lock nut on the barrel adjuster before making any adjustments.
After completing your adjustment, tighten the lock nut and replace the pulley cover.