Chance uses a beach theme to describe his relationship with this girl. He seas, (sees), her have have rough times, but she always gets through them.
Chance continues with the beach theme, and cleverly makes beach sound like beat . To beat your demons, means to face your fears. He continues this with shore instead of sure. No matter what, he’s got her back still.
The fact that her back was sandy, shows that the girl really needed some kind of help. Fortunately, Chance helped her out by helping her beat her demons.
Chance is saying that he hopes this “shorty” is willing to have sex with him. The phrase “goin” means willing to have sex. Like Chance other Chicago based rappers such as Sicko Mobb use this same term.