Many text strings can be translated within the individual CommerceKit module settings. For example
CommerceKit > Ajax search has all the common ones.
For any others, the Loco Translate plugin will work.
Note that Loco Translate’s ‘Relocate’ tab setting needs to be set to ‘System’.
Some text strings don’t appear?
Ensure that you’ve clicked on the Sync button in Loco Translate. This is especially important if you’ve updated the theme and/or CommerceKit, and adds any missing strings.