Complex sentence: A fierce battle was fought outside the wall of Chang'an, where Guo Si personally dueled the famous Lu Bu, even Guo was defeated and was pierced by Lu's spear, he survived the wound and the Liang army pushed Lu back into the city.
Split into simpler sentences: A fierce battle was fought outside the wall of Chang'an, where Guo Si personally dueled the famous Lu Bu. Even Guo himself was defeated and was pierced by Lu's spear, but he survived the wound and the Liang army pushed Lu back into the city.