Brushing your teeth at night especially before sleeping & after eating is more important comparing with morning. Because saliva decreases during sleep by 8/1 & mouth self-cleaning decreases, therefore Leftovers & mouth dryness causes of tooth decay. And brushing your teeth in the morning after waking is often to get a refreshing smell, which can be replaced by mouth wash.
Generally, it’s recommended brushing teeth at least twice a day in the morning and evening, preferably 30 minutes after eating.