I use the Anker Powerport+5 with power delivery hooked to my galaxy s8 which supports QC 2.0 and it show fast charging
Not sure about the c5 but try this
How to enable Fast cable charging on the Galaxy S8
Fast charging can be turned on and off in the settings. To make sure it's on, go to Settings > Device maintenance > Battery > Advanced settings and toggle on Fast cable charging.
With this enabled, when you plug your Galaxy S8 or Galaxy S8 Plus into the provided Adaptive Fast Charger or a Qualcomm Quick Charge 2.0 charger, it should take you from 0 to 100 percent in approximately 2 hours.