I don't know if the imaginations of commenters here is impressive or if their fantasies are mostly a bit sad.

Nancy is pregnant, a drug addict, a hostage, Sasha's love child, a secret agent, a guy in disguise... any of or all of the above.

Adeline is in love with Dasha, but living with Markus only for the apartment, Dasha's hidden lover, Angie's love child... any of or all of the above.

Dasha is Masha's romantic get-away partner, a master chef, a hairball from Sasha's shed chest hair, a rent-a-bitch with no off switch... any of or all of the above.

I think that I have read some variation of every one of these facts here, and some that were even a bit more far fetched and outlandish than the ones listed. 

https://youtu.be/jXatc1yZtCA?si=dP2mdWt676Yhm-bo

I believe that Sasha isn't coming back soon because Nancy is bout to give Adeline a massage.