Can I charge my Galaxy S9+ with a laptop charger I was wondering if i could charge my Samsung Galaxy S9+ safely with a USB C laptop charger.

here's what is says on it:

INPUT:100-240V~1.3A 50-60HZ
OUTPUT:20V--2.25A/15V--3A/9V--2A/5V--2A



For Lenovo information equipment use only


Theres a lot more stuff on it but I'm pretty sure thats the only stuff thats important.
The data of the power supply indicates that it is compliant with the USB Power Delivery Standard (USB-PD). If it has an USB logo there should be some sort of "power flash" within that logo to indicate that it supports USB-PD. 

The USB Power Delivery standard defines backward compatibility, this means that by default the charger will output 5V and only switch to 9V, 15V or even 20V if the connected device has signaled by the USB PD protocol that it supports this mode.

Based on the information I found the Galaxy S9 / Galaxy S9+ support USB Power Devlivery, however they don't make use of the modes with higher voltage.

Therefore connecting it to the described charger it should charge with 5V 2A.