Can I use the Huawei Matebook 13 charging cable for my mobile phone (S9)?

Or could it be damaged?

Do you mean the cable or the power supply now? As long as the power supply can't supply more watts than allowed, nothing should happen.

I mean the power supply, sorry

Without problems! This is a 65 watt charger and it adapts to the voltage and current that is allowed by the charging electronics of your S9 mobile phone. There's always communication between the charge controller chips regarding the desired voltage and current strength and the maximum values.

I charge my iPad Pro with a 96W USB ‑ C power adapter, although 30 watts would be enough, but 18 watts would not be enough for charging and working at the same time.