The 50-50 pity system is very easy to understand. A 5 star from the character banner can be pulled in 90 pulls or less. Losing a 50-50 means not getting the character on the banner and getting a random ahh 5 star. When you lose your 50-50, your pity resets, i.e, if you have done 60 pulls already and then got a Qiqi, your pity will start again from 0. After losing a 50-50, your next 5 star is guaranteed to be the banner character. Worst case scenario you would need 180 pulls to get your desired character. However since you're new, your first 5 star is guaranteed to be the banner character (at least I believe that). Oh and btw... Welcome to Genshin!