I need help with a girl?

i am 13, on the verge of 14. i am going to go run a half marathon soon. one of my mom's friends is doing it, with her daughter. she is my age, a bit younger, she is into science, she studies the everglades, walks through swamps, etc. i love science, but am not a nerd, but i mainly do electrical stuff and chemistry, i need some tips on getting her to like me, i've gone out with a bunch of girls, but currently in a rocky patch. i wanna know how to impress her. how should i look, i know to be myself, what should i wear, my abs are showing, ab lines. but not a full six pack, working on it. i am rather fit, can run 8 miles without stopping, do push ups and sit ups regularly, i am rather shy, most girls that i am friends with say i am nice, and they would go out with me, but i'm too young, i skipped a grade. i make straight a's and going to take, advance geometry or algebra 2, biology, advanced reading, german, rotc. when i'm in high school. what should i do, i am rather attractive, or so i think, i don't know what she looks like [i don't care about looks] she seems nice though. what should i say, i am soooo nervous