Original: Following the invasion of Poland, Seyss-Inquart became administrative chief for Southern Poland, but did not take up that post before the General Government was created, in which he became a deputy to the Governor General Hans Frank.
Simplified: After the invasion of Poland, Seyß-Inquart became governor for Southern Poland, but before he started work there the General Government was created, and Seyß-Inquart became a deputy to the Governor General Hans Frank.