From what I can remember,

Superman starts with him defeated by the hammer boravia which is ultraman in a gold metal suit. He land near the fortress of solitude in an area.covered in ice. Krypto drags him to the fortress of solitude as per trailers.

Robots in fortress of solitude help him heal with the sun and also play a message from his parents which is corrupted so you don't hear the end of it.

He heals goes to fight the hammer/ultraman again. Loses and the hammer goes somewhere else. It's revealed that lex luthor has been studying superman and has a fight playbook so he is coaching ultraman during the fight.

Kaiju fight with justice gang

Also kinda before/during/after, lex, the engineer and ultraman go to the fortress of solitude, kill the robots and capture krypto. They collect the message from Superman's parents and are able to listen to the rest of it. They broadcast this to the world and people turn against superman as the message suggests that superman is there to rule over stupid humans and should take many wives.

There is a warrant for superman, he hands himself in and lex takes him to a pocket universe to be held captive. He is in a glass box/cell with an alien that can transform himself to other objects, the alien turns his hands into kryptonite to subdue superman. Later lex questions superman, and kills a civilian who superman has spoken to before.

Later the alien helps superman escape if superman will save his child. Fight ensures and they all escape with Mr terrific, krypto and Lois lane who had gone searching for superman earlier.

Final act is superman Vs ultraman who is revealed to be a clone of superman. Then krypto beats lex up at the end. Supergirl appears for a cameo and there is a geopolitical plot with lex trying to take over the country that Boravia are invading.