to be honest, I never did a translation myself, so I can't give you much more advice.
But here the idea:
When a string is echoed in the application via the function eT('My String') or gT('My String'), the application first look if a translation is available for it. If yes, it shows the translation, else it just echoes the string "My String".
So in English,
normally, it
should NOT need a translation. The string in the source code is already in english.
But, for what I see, there is an english translation file available:
translate.limesurvey.org/projects/limesurvey-25/en/default/
It's logically pretty empty. It seems that someone use it to change some uppercase/lower case issues, like:
translate.limesurvey.org/projects/limesu...en/default/?page=250
Load Page => Load page
So you can use this translation file, and just update the values with a "survey" string.
So, just google to find some tutorial for poEdit. For what I remember, it's pretty easy to use, and have a search function to find a string, like "survey".