There are two rejection criteria here. One is easy to resolve, the other less so.
The first point is that they are not sure that your Aunt is related to you as you say they are, or that they are willing to support you. You are going to need to provide some documentation showing that your Aunt is your legal guardian to cover that, and that your Aunt is willing and (financially) able to support your trip. Whatever this is, you will need to send them.
The second point, and harder to resolve, is that they do not see enough reason for you to return to Ghana at the end of your trip. You have proven that you are still undertaking studies, but that was apparently not enough. They want to see some need to return to Ghana. They comment that they cannot see how you are supported day to day - if you could show that your ability to house and feed yourself was dependent on being in Ghana, that may help. Better still would be, as mentioned, property, a business, or a dependent - something you need to go back to look after. I don't see that you could practically acquire these however.
The UK visitor rules are at Immigration Rules Appendix V