Complex sentence: Geller played in 23 USSR Chess Championships, a record equalled by Mark Taimanov, achieving good results in many and winning in 1979 and 1955 when, despite losing five games, he finished with 12/19 and then defeated Vasily Smyslov in a playoff match.
Split into simpler sentences: Geller played in 23 USSR Chess Championships, a record equalled by Mark Taimanov, achieving good results in many. He won in both 1979 and 1955 when, despite losing five games, he finished with 12/19 and then defeated Vasily Smyslov in a playoff match.