Addition:
In many cases, the istall log will show errors about missing folders "/DesktopModules/..." This indicates, that there are translations in the language pack for modules, that are not installed, so don't worry.
On the other hand, there maybe modules not included in the language pack. Use the resource verifier to be found in host:languages, to check, which files are missing or are for another version. Due to the fact, that the resource files do not have version numers, the resource verifier checks for missing or redundant keys and compare file dates. Missing or redundant keys may indicate, that the translation is for another version, but there is no check, if text items changes are reflected by the translation.
You can alter the translation (e.g. for an outdated module translation) using the language editor to be found in host:languages. This affects the whole installation.
To customize localization for a single portal, use the language editor in administration:languages. You should at least adopt "Terms of Use" and "Privacy Statement", that are found together with all mail templates in file GlobalResources.