Complex sentence: The Diocese of Gambia and Guinea was created in 1935 and in 1951 was one of the five Dioceses (the others were Accra, Lagos, Niger and Sierra Leone) which came together to form the new Province of West Africa.
Split into simpler sentences: The Diocese of Gambia and Guinea was created in 1935. In 1951, it was one of the five dioceses (the others being Accra, Lagos, Niger and Sierra Leone) which together formed the new Province of West Africa.