You can translate LearnDash by following steps. However, some of the strings are already translated in major languages but all translations are user-donated and, therefore may be incomplete.
Step 1: Head towards Dashboard >> LearnDash LMS >> Settings >> Translations
Step 2: Download the .po file by clicking the Po download button. This will open the .po file in a new window. Right click and save to your system.
Step 3: Open the .po file with PoEdit and add your new translations.
Step 4: Regenerate the new mo file via File > Compile to mo… and save the .po file.
Step 5: Add your new mo and po files to /wp-content/languages/plugins/ via FTP or File Manager.
The above steps will apply to LearnDash v2.5.5 and later.