Just had the weirdest interaction

2 days ago I (m21) was attending to my 2⁰ karate class, and I tried talking to a girl, except i wasn't talking, until she started the talk then I could talk but it still feels forced and it didn't flow.

The next day I thought about sending a message but I don't know if was a positive interaction, and felt weird if I got her number from the karate's WhatsApp group, like "without" her permission or something, also I'm from Brazil and yesterday was our valentine's day (sorta) and didn't meant to look like I was going to fast, if there even were somewhere to go.