Welcome to Android Central! Just to be clear, you're talking about the Huawei P Smart, and not the P20, correct? They're different phones. But as Galactic Zoo, pointed out, the phone is dual band, and is therefore capable of both 2.4 GHz wi-fi and 5 GHz wi-fi:
https://www.gsmarena.com/huawei_p_smart_2019-9409.php. Remember, this is different from "5G", which refers to mobile data (i.e., 2G, 3G, 4G, etc.).
Go to
Settings>Wi-fi, then look for Advanced settings. Do you have a Preferred Network Type option? If so, make sure it's set to Automatic, and not 2.4 GHz Only.
