Complex sentence: The resilient Austrian was standing and talking to other drivers right after the accident and his injuries were initially not expected to be serious; although he had been severely burned and had been breathing in toxic fumes, which damaged his circulatory system.
Split into simpler sentences: The resilient Austrian was standing and talking to other drivers right after the accident and his injuries were initially not expected to be serious. However, he had been severely burned and had been breathing in toxic fumes, which damaged his circulatory system.