Phrases for translation used on front-end are here:

• language\en-GB\en-GB.com_splms.ini
• language\en-GB\en-GB.mod_splmscart.ini
• language\en-GB\en-GB.mod_splmscourses.ini
• language\en-GB\en-GB.mod_splmscoursescategegory.ini
• language\en-GB\en-GB.mod_splmscoursesearch.ini
• language\en-GB\en-GB.mod_splmspersons.ini
• language\en-GB\en-GB.mod_splmsupcomingevents.ini

Some phrases may be also in template language file.

and for back-end:
administrator\language\en-GB\en-GB.com_splms.ini

You can copy those file(s) and rename to your language code, for example:
de-DE\de-DE.com_splms.ini
then translate inside all phrases or only selected.

You can also use Joomla Language Override system to translate only selected phrases as well.