What Is the Proper Way to Merge Usermeta Table to a an existing WP Database?

I'm currently testing some features on a sandbox environment. I have an existing production website and I'd like to ship my production users and other related tables on new sandbox environment. While doing this, I'd like to retain users on sandbox. I have used CSV export, editing IDs through Excel but importing is adding extra quotes or splitting columns due to commas. Any ideas? I know that some of the issues are caused by my regional settings on Windows however I'm pretty sure I'm missing some important details as well.