Language courses are fairly limited in and around Accra. A handful of schools will offer classes in international languages, with French being the most common. Surprisingly, very few schools offer courses in popular local languages such as Twi, Asante Twi or Mfantse. For learning these languages, you are probably best to seek out a native speaker willing to teach you.
Although formal opportunities to learn local languages are somewhat limited in Ghana, it is very likely that you will be able to partner up with a native speaker to trade language lessons. This is a great opportunity to learn not just the grammar, but also the customs, culture and area more broadly. Questions about gift giving, festivals, nightlife, and greetings can be addressed without worry. In the best-case scenarios, an exchange partner is not only your ambassador, but a friend.
Try looking for a tandem partner through EasyExpat's Classifieds.