That 2nd picture should really confirm it to yourself. If you're feeling brave, do the same shot with wet hair after putting a comb through it, I warn you that there may not be a lot there, but if that's what you need to be convinced.
But a "mature hairline" stays pretty much in tact, and in most cases a mature hairline will happen early in life (early 20s to maybe past mid-20s) and it will stay at that same point, but what you have in the 2nd picture, if you can imagine a line going from temple to temple, over the top of your head, and everything in front of that line is clearly thinning and will continue to do so back to the crown. A "mature hairline" isn't related to thinning really.
At 36 I don't know if your chances of growing back that hair are great, I mean I literally don't know either way, but yes you need to use minoxidil at least, and I'd say finasteride. Talk to your doctor as well. Maybe it's not the worst thing if you don't regrow any, if you already aren't noticeably bald then as long as you maintain hair you're still a normal guy to most people.
I'm also not great at Norwood judging but I'll guess a Norwood 2.5.