Do the Don downfall first Basically get Cassie kidnapped by leading them to Cassie then Talking to Fawn, Arlene, The Beggars, and Lin Lin, this is a Save Load Repeat quest save before you do anything, messing up whole trying to break in will give you a Bad end.
Or if you have done all of this just talk to her a lot go to a date or give her "Fish"
To do the Don quest go to the. Slums in New ark then simply not pay the Bridge toll sleep go back to the slums then say to the Don "Grunt Work" then he will task you to find Cassie, simply go to her Safehouse then talk to her "About the Don" leave go to Ark come back and she would have Disappeared going back to the Don you can get paid or you can reject it, i Rejected it i dont know what will happen if you do accept it. Then Speak with Fawn if you dont have her yet just Search "Fawn Wiki" and a guide is written there. Fap in 5 different Bathrooms, Arlene is pretty brutal in her Scene mentioning Bleeding and all that stuff basically Masochism Kink, but you dont need this just talk to Arlene cause a Riot by paying a Beggar 2k credits then sleep, then find the Beggar in the "Gentlemen Club" he will give back 5h credits use that then pay the Beggars again to cause a riot, talk to Arlene and then attempt the Break-In. Arlene might Rape the Don we will never know i assume that because of how she treats you when you get Caught. PLEASE GET LIN LIN she is a free pass on the first choice!
And thats all i think Correct me if im wrong!