Try to change your charger set first. I recommend baseus 65watt charger, it should be "fast charger" . If "fast charging" doesn't appear on your screen please go to nearest service centre in your town.
My side port isnt fast charging and lower port sometimes charges fast sometimes doesn't....also charging stops randomly many times then I have to reconnect type c to restart charging..... Switching off and on charger doesn't work..only replugging type c