I was moving the weight just slightly slower than necessary for the sake of allowing you to see how I execute the lift. My upper arm path is not unnecessarily wide, but at a fairly obtuse angle from my ribcage. It’s different for everyone, but start with a relatively light weight and go through a series of reps until you find which one puts/keeps the tension on your pectoral muscles. I’d say start at about 45° and go in or out from there.

Also, notice my transitions. Not bouncing off my chest; not popping the weight at the top in a hurry to get to the next rep. Feel the weight at each step of the rep. It’s not a race for reps. Instead, adjust the load to be just at, or slightly past the rep range you know experientially you can get.