debug Google Apps Script within a Google Sheet

We have a Google Sheet with Apps Scripts to: - maintain the sheet (delete lines upon defined criteria). Existing scripts kind of work but need to be at the bottom of the script list (I am a newbie in Google App Scripts so, I don't get how this work really). - compute duration between 2 addresses using Google Maps API (based on [login to view URL]) for many lines (~1000 lines). Goal is to limit the calls to the API to avoid too many calls for the day. Your work would consist in debugging the existing scripts or propose a better design for them to work.