Girl open with just 'hey'

Hi guys,
a lot of girls open a conversation with me by writing just 'hey', so i follow up with 'Hey, what's up?' and i noticed that 90 % of the time converstation is dead at this point.
How do you respond to such a message. I'm in Poland, so maybe it's only that bad here. And i'm like top 5% of Tinder in my location, aall girls I've met and hookup said that, so it's not about look