I'm using games to learn foreign languages (currently German) so I'd like to rewind and look at the conversation log if possible. Sometimes the conversation also goes by too fast. However, I didn't find any option to do so. Is there any option or mod (I'm playing on PC) that would help me achieve this?
No, there isn't any way to do this in game. There is also no mod that allows you to replay conversations. I went through all of the audio and UI mods in nexusmods and couldn't find any that allowed this.
There was also a couple steam forum posts that talked about rewinding dialogue and the closest answer that was actually given was to create a save state or quicksave before your conversations so you can always quickload and redo the conversations.