How can I play AGAINST my friend?

So the problem is that I figured out how to add my friend to party, but we can only play 2v2 or higher but not 1v1, why is that?!
I want to teach my friend how to play and let him practice on me rather than going 2v2 against some experienced players and get early rushed in no time. That literally ruins new players experience.

In matchmaking, you can’t choose your opponents. Once custom games comes online, you can create up a lobby and set yourselves against each other.

The beta may not be the best client for that. Use the Classic version for now.

Use classic Frozen Throne or RoC to train. It’s the same game, they are compatible and will stay compatible. Or else wait for custom games in beta next week (I guess).

TBH you should not be treating the beta as a demo or a new player experience.

Beta is for testing bugs and making sure the game runs on your machine, and providing that feedback back to Blizzard.