Goku fought Beerus the bored and glutton cat-shaped god of destruction. He lost but the earth was spared because Beerus took a liking to people and food there.
Goku is now a "super saiyan god" and trains with Whis, an angel that is actually the teacher of Beerus. Vegeta is there too. Both saiyans evolve further and become Super Saiyan Blue.
Freeza is resurrected and wants his revenge. He trains for the first time in his life reaching SSB level with his new form "golden frienza". He is defeated again by Goku.
Another cat god of destruction in another universe, who is also a rival of beerus, is gathering "super dragon balls": planet-sized more powerful balls.
Beersu is not okay with this as some balls are in his universe. They can't fight each other or the universe would be destroyed so they make people from their universe fight. Goku's universe wins.
At the end of the tournament Goku gets to know the highest authority of the universe, a dull, dumb, childlike god who is known as zeno. Every god including gods of destruction is afraid of him, but Goku is relaxed and Zeno decides he likes Goku.
The tournament is broadcast on "Godtube". A deity named Zamasu who is racist and definitely homosexual decides to steal Goku's body to kill all humans.
He then travels to Trunks future, where he allies with his future self.
Mumbo Jumbo timeline drama that can't be explained in a few words, anyway it ends with Zamasu dead and 2 zeno, one is from the future.
The two zeons together decide to destroy the weakest universes so they force every universe to join a new tournament, losers will be erased.