I had the same issue and fixed it with a suggestion from https://www.gosunoob.com/assassins-creed-valhalla/defensive-measures-mission-bugs/: (https://gosunoob.com/assassins-creed-valhalla/defensive-measures-mission-bugs)

"Switch the game to English, or any other language, load the last save that doesn’t contain words “Defensive measures” and redo the quest. After the attack, an option will appear to speak to the Builder."

Before you talk to the builder... SAVE THE GAME and change back to a language you understand! You will have to make a decision when speaking to the builder and not understanding what he says will be a problem. It was a little glitchy and I still had to fight 3 mobs after the shield had turned green and the Builder said it was over, but that was easy and beyond that it worked like a charm.

P.S. - Be sure you know how to get back into settings and change the language back to what you prefer by remembering what is where or taking a screenshot, etc. or you may have a hard time figuring it out in a language you don't understand.

I had the same issue and fixed it with a suggestion from https://www.gosunoob.com/assassins-creed-valhalla/defensive-measures-mission-bugs/: (https://gosunoob.com/assassins-creed-valhalla/defensive-measures-mission-bugs)

"Switch the game to English, or any other language, load the last save that doesn’t contain words “Defensive measures” and redo the quest. After the attack, an option will appear to speak to the Builder."

Before you talk to the builder... SAVE THE GAME and change back to a language you understand! You will have to make a decision when speaking to the builder and not understanding what he says will be a problem. It was a little glitchy and I still had to fight 3 mobs after the shield had turned green and the Builder said it was over, but that was easy and beyond that it worked like a charm.

P.S. - Be sure you know how to get back into settings and change the language back to what you prefer by remembering what is where or taking a screenshot, etc. or you may have a hard time figuring it out in a language you don't understand.