If I disable WP multisite feature, will it also erase everything that's been on my site?

I just want to confirm this before doing anything.
I installed wordpress on my site with multisite enabled and I didn't notice it right away.
Now some important plugins are not working because of it.
But I hired someone to build my site so if anything goes wrong, I'm not sure I'll know how to recover everything besides those that's been covered by database backup.
Has anyone of you experienced doing this before?
Any nice links to tutorials you can give to me?
I searched but not technical related threads about this.

make sure to keep a full backup of your database and also download the folders using filezilla.

Thanks, I did that. So do you know if there's any chance that any of the work already done be deleted if I disable the multisite?