Why was the GUANethnic group were first settle in Ghana?

The premise of your question is not correct. There is no known or documented ethnic group called the "GUANethnic" group that settled in Ghana. Ghana is home to various ethnic groups with rich cultural and historical backgrounds, including the Akan, Ga, Ewe, Mole-Dagbani, and Gurunsi ethnic groups, among others. Each of these groups has its unique history and migratory patterns, and there is no evidence to suggest the existence of a "GUANethnic" group.