This page of the guide to Assassin's Creed Valhalla Dawn of Ragnarok describes World Events in the region of Gullnamar.
Location: Western part of the region, right by the harbor.
In order to complete this mission, you need to purchase an upgrade to the Power of Rebirth Instant Horde skill.
The entire side mission begins with a conversation with a woman. She explains that she was not able to say goodbye to her beloved. Your job is to bring him to life so they can talk.
The man dies several times during this conversation. Revive him as many times as is you have to (should be three approaches to this). However, if you are moving away from the couple, the skill's time passes and they stop talking, which may require even more attempts.
When finished, talk to the woman. This will complete the mission and give you the key to a nearby building.
Location: Eastern part of the region, south of Uldar.
The mission will begin with a fight with a bear. You must defeat it to save a man in distress. If you don't do it the first time around, you don't have to worry. This event will be active all the time and you can return to it whenever you so please.
After defeating the bear, talk to the man. He will tell you about the cursed ring, and your task will be to accompany him to the mountain. The quest will end when Fordri throws the ring into the lava.