Removing a wordpress multisite installation and preserving the database before migrate to nginx

Hello, I have a wordpress multisite installation, and I need to remove the multisite, and keeps just the site ID 5 (leetdoc.com/br) in the main address (leetdoc.com). So I follow this tutorial to remove wordpress multisite installation: premium.wpmudev.org/blog/uninstall-multisite/, after that I dropped wp tables post, terms, term_taxonomy etc, and changed the tables wp_5_ to wp_. My site became extremely slow to open pages, his aesthetic was greatly affected, images did not load, so I was informed about the serialized data in the database, and that I should not change the database manually.

I do not intend to migrate the multisite to nginx, just a single website (ID 5), so what is the best option to preserve my data?

p.s.: I’m disregarding the option of buying a plugin to do this, and learning to do at hand.

Daniel