Simplify the following text for a Grade 4 native English-speaking person.
Original: Safin began his professional career in 1997 , and held the No. 1 world ranking for a total of 9 weeks between November 2000 and April 2001 . He won his first Grand Slam title at the 2000 U.S. Open after defeating Pete Sampras , and won the 2005 Australian Open , defeating Australian Lleyton Hewitt in the final .
Simplified: In 2000 and 2005 , Safin won the US Open and the Australian Open .