I would like to create a child theme, but I have already made hundreds of modifications to many php files. To translate the entire page in Spanish.
Do you think I can create a child theme keeping all those changes I've already made?
I need to do really because i have 3.3 Version of theme.
You should create a child theme and copy over the files you have edited there. This will allow your changes to survive future theme updates. If you directly edit the theme’s files, all changes will be lost once you update.
Have a look at this guide to learn more about child themes and how to create one www.cssigniter.com/ignite/beginners-guide-child-themes/