Hi Doash,
When editing words, please make sure you save your translated word using the "Save As" button - this will let you save your Arabic word as a separate "word file" and won't overwrite the original English word.
In case you need more details about making your own translated lessons, you may refer to this article:
http://support.brillkids.com/entries/20622132-How-can-I-translate-my-Little-Reader-English-Curriculum-into-the-language-I-want-to-teach-