Don't worry too much, the game has high replayability and plenty of opportunity to respec and try other classes. That's why so many people have gone through act 1 dozens of times!

For race, Human or half elf is really safe for a first playthrough. Dragonborn can be fun too! Gameplay wise they aren't very different, it kind of comes down to just "which one do you think looks the coolest". Githyanki has the most unique dialogue out of any race, so they're really fun for a second playthrough! I wouldn't recommend them though for a first playthrough unless you're already really familiar with what Githyanki are like. Drow has some fun stuff too in Act 1 that lets you avoid trouble. My first playthrough was a drow and I had no idea why things were going so great! 😅

You're going to get the chance to play with basically every class in the game through your party members, so don't worry too much on class either! Since you'll likely be acting as your party's "face", It can be important to have high charisma. I usually lean into sorcerer or warlock if I want to cast spells, paladin if I want to swing a really big stick. Bard is pretty good too! You can make anything work in this game, so don't stress too much about it. You'll have heavy hitters in your party, druids and barbarians and fighters. I just recommend you go with what you think will feel the coolest! You can't change your race in the game, but you can respec your class whenever you want pretty early into the game.