High Valyrian Questions
1.Is there some place where we can use High Valyrian? 2.How was it invented?
Not really. I mean, yeah, there is the discord server. But apart from that it's just a hobby. And there are a few lines in Game of Thrones that don't have subtitles that you can understand when you learn HV.
David J Peterson invented it for Game of Thrones. There are a lot of resources out there on the Internet about the details (his blog, twitter, the Ice and Fire wiki, loads of interviews, etc.). But basically he started from a few words and phrases and names and a bit of culture and invented a full language around it.
For 1, there's this place: https://www.shakeshack.com/2019/04/11/fire-meets-ice-try-our-limited-edition-game-of-thrones-menu/ which does actually have some menu items in High Valyrian but that's about it - ValyrianSoGu answered 2 already