HELP! Redirecting to already existing blog site

Hello, I had already once set up a site on my url/blog page. I then created my official site on just my URL, but I would now like to move it over to my url/blog page. I went in and attempted to redirect it, but it didn’t move over my posts at all and now I can no longer log into the old site’s Dashboard!

I’m SO lost and confused, can anyone please help me figure this out? I try to log back into my original site’s Admin panel, but it keeps redirecting me to the /blog site and not even the Admin panel for that site any longer! HELP!!