blowjobs

so me and my bf recently started having sex. i told him before that i never sucked any of my exes dicks. so i asked if he could teach me, you know how he likes it. so i been watching porn on how to and i sucked my bfs dick. later i asked him how was my first time sucking dick and he gave me a 80% but i was scared about choking on it so i wasnt putting it deep into my throat. i just want to know how to get my 80% to a 100%. i know i should ask him but are there tricks to help with gagging or anything that could help?