Don't know much about this smoker but at the price point I suspect it's not going to be very airtight. Also, metal is probably quite thin and flimsy so a lot of the heat will be being lost through that before it gets up to where the food is especially in the colder weather we're having at the moment - make sure you're using it somewhere reasonably sheltered from wind etc.
What are you measuring temp with? The analogue temp gauges on these units (even the expensive ones) are usually not very accurate. Get yourself something like a Maverick ET 733 for fire and food temp. Great kit and peace of mind that the chicken is properly cooked and no-one is going to die
Are you using water in the pan? If so, replace with sand or a clay saucer covered with foil. The water tray is not for keeping food moist, it acts as a heat sink to keep from getting too high.
A chicken is going to take an hour or two so rather than 4 or 5 for something like ribs. Therefore you don't need the minion method for lighting coals and keeping them burning for a long time. I would light all coals in a chimney starter and the. Chuck them all lit in the coal basket, put the unit together with clay saucer in water pan and see what temp you get it to.
Finally, remember with smoking to get the food on at correct temp and then leave it there. Resist the urge to lift the lid and check as you're just letting all the heat escape - if you're lookin' you ain't cookin'