Link to it, clarification: https://community.brave.com/badges/102/-
How do I get this badge?
I’m super curious, I want to take the test/guide, this is interesting!
And can I write here in Ukrainian, forgetting about English & the translator?
@umpy,
You’re welcome to write in which language you prefer, just know that you’ll likely get translated responses in return 
That badge is a bit antiquated/unnecessary – it’s basically obtained by following the Discourse (the forum software running this Community) guided tutorial. Not super relevant to Brave – I myself don’t even have it.
If you do want to go through it anyway, you can send DM to @discobot saying:
@discobot start advanced tutorial
Of course, I know this is about this community and not the browser itself, thanks for telling me how to get there.
And please tell me how to start DMs with other users, like I write first?
You can’t. This was removed a long time ago because of all the scam accounts being made here and pretending they were from Brave. Only people from Brave or some select few active helpers are able to start new DM.
Mailbox is kind of hidden too, at least in the UI. But you can navigate to it by going to something like https://community.brave.com/u/name/messages. Just replace name with your username. So like yours specifically would be https://community.brave.com/u/umpy/messages. Otherwise you’d only be able to see it when someone messaged you and you get a notification, at which point notification would take you to the message.
Again, this only lets you see messages that has been sent to you and you can then reply to those. But you won’t be able to start a DM with anyone new.