How to protect myself from Girl games?

Pls help me how to react to some games played by girls , especially online social or chatting app and websites. The story: a few weeks ago I asked here about making new friends online, and some fellows here told me to make account in some social or chatting websites, i did that. I started looking for girls near to my place so we may have better chance to hang out after a while, but after talking in very friendly way with some girls for few days, they asked for WhatsApp , Skype, messanger or line app. s so we can be in contact by instant messages instead of emails. Then it seems like after she received this account she disappear, then another girl appeared and started talking to me , which i think either her friend or same person with different profile, then same story repeated again, but i became more suspicious about their behavior so i didn't use my primary app , instead used new accounts. The new girl also did the same , they talk then ask for instant messaging app then disappear without using it. I made sure they won't see private info in these app. s. But what is the benefit from these tricks?
Some of them seemed very friendly and i saw some evidence they used their real name, then they act like a group of friends or same person who is trying to collect info from me gradually by shifting from one account to another.
In real life i heard that some girls send their friends to test her lover if he will cheat on her !!! And once i heard they call from fake numbers to do the same as well!!
Why girls do these games. How to react? And how to find a real friendly girl who is genuine and will not come in different name the next time. Do they sit and exchange news about these nonsense behavior?
I appreciate good clever answers to solve this issue. Thanks
How to protect myself from Girl games?
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