CPR is for inconscious, non-breathing folks. While calling 911 loudspeaker on, lay the person on a hard surface and kneel beside. In a tripod position, clutch one hand upon the other, and aim right beetween their undressed tits with your lower palm, pushing down and releasing 1/3 of the chest /don't crush them/ on a staying alive "ah-ah-ah-ah" rythm. Non stop. Hopefully you're not alone because that shit's exhausting.

Tips: Check the pulse at the the wrist, not at the neck. But breathing = pulsing in general.

In case of a seizure keep your distance, gently talk to them. After it's over, lateral position and check breathing. CPR if it stops. Stay by their side, keep'em warm.

Fear not, 911 will guide you but know the basics, avoid doing ankward dangerous shit like that dude.