Simplify the following text for a Grade 9 native English-speaking person.
Original: Unsatisfied with Opeth 's slow progress , DÃ ring and Dimeo left the band after their first performance , and were replaced by guitarist Kim Pettersson and bassist Johan DeFarfalla .
Simplified: DÃ ring and Dimeo left the band after one show and were replaced by Kim Pettersson on electric guitar and Johan DeFarfalla on bass guitar .