Yes, you can use this power supply to charge your Samsung smartphone, as it is compatible with Power Delivery (PD) products via USB-C. However, make sure your smartphone supports PD charging to get the most out of this power supply.
Yes - I had to buy two via Digitec from Conrad. So I have one unused….
Remember the RPi5 will work directly with the 3A PSU but only if you use a microSD card.