Try this ...
Make sure your USB type-C cable between charger & mobile are not tangled or twisted as well the cable are plugged properly to the charger as well to the mobile socket ...
make sure charging information switch on main mobile screen to notice any changes occurs ....
settings >>> Battery >>> Charging settings >>> Activate slide button of Show charging information ....
When you plug USB Type-C cable to your phone first time notice main screen notification that appears if it is Normal or Fast charging, if it was normal unplug/plug again after 5 secs waiting period the USB Type-C cable to your mobile, you should notice a change appears on main screen declaring that the charging change to be Fast charging ...
