Loved the game but small problems IE the assassin quest with you simply being out powered and softlocked with no way to go back to before the quest started and now I'm essentially locked and can't progress the game any further
Do you have any auto save or save file at all, to go back to? I recommend you save every now and again, since there's a lot of choices in this game, which can end in a game over screen/end the game, like not being prepared for that quest.
Also, if you're struggling with that fight, I recommend you buy the dagger from Bront beforehand, as it makes that fight very easy and allows you to break his shield without any effort.