My [18M] first threesome with friends [MFM]

I was 18 at the time (19 now) and still fairly inexperienced sexually. I had a GF and had sex previously but was on the dating scene again after we broke up. Essentially matched with a super cute, petite girl online and thought she looked familiar. I dug around and recognized her from school AND that she was dating a guy I kinda knew. I awkwardly asked about that and said that they were open sorta and he was cool with her finding a 3rd to join. I ennded up talking with them more at school and, she said she “liked me” and we flirted, even traded nudes (all 3 of us even). Katie was slim with small boobs but perky nips and a trimmed pussy, and Jake had about a 6″ dick and slim body as well. They were surprised I was big for my size (I’m just under 6 ft and about 170) and even bigger than her BF by maybe an inch or two. Eventually they agreed to a threesome.