hello, I recently bought a weber jumbo joe and was excited about smoking meat with it. I bought a chimney starter, a hinged grate, charcoal baskets, and the inkbird Bluetooth thermometer. the other day I attempted to smoke a 3 lb chuck roast. I started charcoal with my chimney, dumped it into a basket, set the meat on opposite end of grill and closed lid. I was able to keep temp at about 250-275 for about 2 hours. When the grill temp started to drop, I added charcoal. I had a difficult time from then on with keeping the grill temp above 200. After many hours of monitoring grill and meat temps and adding charcoal when necessary, the internal temp of the meat never exceeded about 160. I finally gave up and removed meat after about 9 hours, but it was awful. Very tough and chewy. What did I do wrong. Why could I not keep grill temp up? I adjusted the vent many times but to no avail. Any advice will be appreciated, I will not give up. I am determined to get this right. Thanks in advance.