if you did not know how to build the gym, you have to go to Hana's world and gather Sexual Energy Y there. then you can talk to lily and discuss plans about building a gym overnight, which then allows u to get Tifa.
i attached my save which is at the dialogue with Lily to start the Tifa quests. saves are in WelcomeToErosland-0.0.13-pc\game\saves if you're unaware.