Complex sentence: Astrid becomes very close friends with Niki and Yvonne and has sex with Rena's boyfriend Sergei, one night after getting high on acid with Niki, Astrid begins to have memories of a woman named Annie.
Split into simpler sentences: Astrid becomes very close friends with Niki and Yvonne and has a sexual relationship with Rena's boyfriend Sergei. One night after getting high on acid with Niki, Astrid begins to have memories of a woman named Annie.