Moving Wordpress multisite from folder to root

Hello!

I have the website 'littlerenard.com' installed on its own folder.
However, today I activated Multisite, and created a subdomain. On the way, I found out that Multisite doesn't work if the main install is not in the root.

I would like to safely move the wordpress installation of 'littlerenard.com' in the root, then continue with the multisite.

Could you please give me some advice?
Notes: There is one subdomain created, but not really important, I also want to get rid of it.

Thank you!