Simplify the following text for a Grade 8 native English-speaking person.
Original: Instead , his younger brother , IBF and WBO heavyweight world champion Wladimir Klitschko agreed to fight Haye the same date in Gelsenkirchen , Germany .
Simplified: A few weeks after the fight , Wladimir Klitschko , the IBF , IBO , and WBO heavyweight champion , said he wanted to fight Haye .