will multisite in subfolder influence wordpress installation in document root?

Before I start creating a multisite environment, I would like to be sure that my current wordpress installation won’t get messed up.

About a year ago, I published a wordpress website on my own domain. The site has been growing and now it would need separate sections, each with their own theme and blog. Actually, even the group of registered users could be different.
I think a multisite could be used in this situation.

However, my time to work on the website is limited and that’s why I’m a bit anxious to enable multisite on my current website. From what I’ve been reading, a lot of pathnames would have to get changed in order to keep the site running.

To avoid this, I installed another wordpress in a subfolder of my document root. That wordpress is now ready to create a network of wordpress folders each in their own subdirectory.

In the ‘setup Network’ screen, I read that the server address will be the url of my main site, where I would have expected it to be the url of the subfolder in which I intend to create my multisite.

Hence my question: will my current main website get messed up when I click the ‘Install’ button? If so, I may need to reconsider the option of creating a multisite or carefully plan the transition of the current website to a multisite at a later time.