This video has inspired me to spend next week doing a 6 day paragliding course. The only downside is the school near me don't teach paramotoring.
Could I buy (and safely use/self-teach) a paramotor after learning to paraglide?
It's never safe to teach oneself to fly anything. Aviation pioneers did that out of necessity, but many died or got badly hurt doing it. Training gives you the benefit of decades of hard-won experience without the underpants soiling moments and broken bones.
You are talking about going from being an inexperienced paraglider pilot to a complete novice powered paramotor pilot without the benefit of any mentoring or coaching.
It's a bad idea™