So, I decided (via a virtual machine) to download debian. Everything seems to be working fine, except when I open debian, it takes me to "yunohost login". I tried everything I could think of, from "root" to the username it told me to put for the user, even "admin". Nothing worked.
Where'd you get the image? It sure seems like you installed a yunohost image of Debian. See here for the default credentials to try logging in: https://doc.yunohost.org/admin/command_line/
If you're literally unfamiliar with the technical process of this, I suggest you go back and read a guide, so every step very literally, and then come back if you have a problem.
It's very obvious that's you're skipping steps or ignoring something.