Uploading new theme into word press declined

Hi there can someone please help me understand why my wordpress website is refusing to upload new themes? It keeps saying failed. Is it that there’s no more space? If so, how can I clear all the themes I don’t use and just open up more space to upload the one I want? I am currently using enigma and wanted to shift to Business lite theme. Any help will be greatly appreciated as I am not a tech genius yet 🙂
Thanks