A few month ago, I join a adult friend finder, and I contact one girl, and she invite me to join a swinger club and be her sex partner, then we talk in the other communication app(this app is free, like a whatsapp), then she explain me some rules and some information, after that, she say I need to contact her admin and understand how to pay the membership Id, and I contact, then the admin explain how to pay（ PS. All payment is pay by cash, no need to use credit card, no need to go to some website to join the member or something）after that she ask me pay again and again （reason：they need to use step by step or something), and now I need to pay again because I do something wrong, I don't know is that scam or what.

PS:
1.a lot of photo which is they give me can find in facebook and website, but I think all photo was posted by that girl
2.They can say her name which is match with Facebook
3.But in Facebook, they post some photo is sure not in my country(I already ask this one and they have reason)
4.Admin was help me to pay some payment

It's a SCAM!!

Flag: pay for a "membership id". Its one of the oldest tricks to get unwitting people to fork over $$
Flag: Cash no ccd needed and even if it was payable by ccd. Still a scam, for now they have credit info!
Not sure what the "admin part" was all about, but no matter she just trying to rip you off.
The signs are all there in your post it's nothing a scam.

Remember Knowledge is Power

Len

What was the name of the club they gave you?

If you are living in the DFW area its the Lover Louge