Simplify the following text for a Grade 6 native English-speaking person.
Original: In less than a year , he captured Fort Provintia and besieged Fort Zeelandia ; with no external help coming , Frederick Coyett , the Dutch governor negotiated a treaty , where the Dutch surrendered the fortress and left all the goods and property of the Dutch East India Company behind .
Simplified: In less than a year , he took Fort Zeelandia and made an agreement with Frederick Coyett , the Dutch governor . The Dutch gave him the fort and left all the goods and property of the Dutch East India Company behind .