At this time, there is no complete translation of the Rules into English.
Eressea started out with German rules only. We have made a few attempts over the years to create an official translation, but none of them reflect the current state of the game.
The authoritative rules are those found on the German pages of the rules wiki. This is currently being translated into English, and we encourage volunteers who want to help with the translation to join the #documentation channel on our Discord.