Pretty much every loser I talk to about girls mentions that they "don't know what to say" around girls. They tend to run out of topics quickly, and think they must have some social deficit. It's hilarious because they don't realize what's actually happening: girls are sabotaging their conversations. They don't want the interaction to go where the sub-5 wants it to go, so they give him nothing to work with. Here's a great example from master PUA and world's leading cringe coach Jonny Berba:
The PUA has to ask question after question -- introduce topic after topic -- while the girl gives short, monotone responses that add nothing to the conversation. He literally hits everything from work to dating to where she grew up, and she offers absolutely nothing in return. This is what girls do when they want you to go away. They don't actually reject you -- they just passively kill the conversation. (Particular lols at the "close" in this video where Berba asks for a date and she sidesteps by saying she's going to be out of town for two weeks.)
This is why there's no such thing as good social skills. If the girl doesn't want the interaction to continue, she will give you nothing to work with and leave you "running out of things to say." If she thinks you're hot, she will actually contribute to the conversation, and suddenly everything you say seems to work. And when you "run out of things to say" she'll pick up the slack.
tldr: Just lol at social skills boyos