I plain English
I use two servers and two setups, so I made two pics with arrows to show that to look for
The place that you keep your databases = PHP Admin
Each Table has drop-down list, and language setting.
When I took on my site many were in Swedish
I had to take each table jos_XXXXX and set it to UTF-8 Unicode (utf8)
I don't know if I am right but you did say "both swedish AND english lang files"