How can I keep the same layout (template, font-style, size...) when I switch from FR to EN without having to modify the EN page directly?
Here on exemple of the problem when you switch from FR to EN : hidden link
Now, regarding your request, sometimes, with content builders, there can appear issues like this for multiple reasons (sometimes some of the modules from the visual builder that are used are not compatible with WPML yet, some updated that have been recently launched with that page builder are not still 100% compatible with WPML, etc.).
In that situation, here are the steps that should make things work as expected:
1. Create a full backup of the site
2. Delete the current translation by switching the flag at the top, go to pages, click "delete" on the page translation, then go to trash and remove it from there, too
3. Switch the language back to the original/default language, from the top of the backend
4. Go to WPML > Translation Management
5. Select the page that you want to duplicate, select the language that you want to duplicate the page in and click duplicate
6. Now switch the language at the top of the backend, go to Pages and click "Edit" on the newly duplicated page (it should open it in the same editor that you created the initial page in, so it should take the layout and instead of using any of the WPML editors, you can manually translate by using the initial editor that you used for the initial default-language page)
Situations like this are a bit tricky as depending on multiple things that are/or are not compatible, you can end up in situations like this where the best solution is to Duplicate a translation and manually translate the text afterward.
Sometimes, there are also custom fields that come with a theme or with the content builder that was used to build up the pages and due to the fact that the custom fields are not set to "copy", the correct layout is not carried over to the secondary language.
Regarding the translation, when you are using that method, you are overwriting all the existing translated content, that's why I recommended you to create a full website backup first, in case you still need to restore to an older version.
My recommendation is to either to move the translated content into a document first or to create a duplicate of the current page with a plugin like this (https://wordpress.org/plugins/duplicate-post/) and then copy the content from that duplication into the original translation.
Well I cannot do it just by duplicating the page as I have more 100 products... Is there anyway to export the translation (maybe directly through the FTP) and then import then after doing the modifications?
