There are advantages to breathing from your nose more than your mouth. As Patrick McKeown, an advisor of the International Academy of Breathing & Health, told USA Today, "the nose is [the] first line of immune defense" because our sinuses produce nitric oxide that is "antibacterial, anti-fungal, anti-pathogenic and antiviral," but our mouth doesn't.
Still, there are ways to achieve better breathing. Yoga helps with proper breathing from the nose, for instance. You might take up yoga to work out or improve your flexibility, but James Nester, a science journalist and author, told the publication, "Yoga was first and foremost a technology of breathing."
If yoga is not your thing, you can also practice breathing by learning some exercises. Healthline recommends trying alternate nostril breathing or belly breathing to practice mindfulness while breathing, which can help reduce stress, increase your lung capacity, and focus on breathing from your nose. It will take time, but these breathing exercises or adding yoga can definitely improve your nose breathing. However, if you cannot breathe from your nose due to other health reasons, you should consult a physician.