I will explain to you what may happened.

There is no delete button for translations. A translation gets deleted when the value is empty. When saving an article, or whatever, the translations system checks the strings that have been submitted for all languages. If the value for a language is empty, or not provided, it is marked for deletion.

en: Hello
el: Γειά
de: Hallo
it: Ciao

If you set de = "" (empty) then the corresponding translation will be deleted from the database.

Example
You have an article title in 4 languages, de, en, it, es
You unpublish Italian language (it)
You go and edit the article. As Italian is unpublished only values for de, en and es get proceeded (there is no "it"). Therefor the saved in database value for it is empty and so gets deleted.
When you re-enable Italian language and go to edit the same article you will see that there is no value for the "it".

If you lost many translations due to the above reason it means that you have the language set to OFF for a long time and in the meanwhile you edit many items.
This is absolutely normal behavior and this is how the translations system works. The deletion of empty/unused strings is in order to remove items from the database not needed any more.

Switching ON and OFF language does not affect translations saved in database. What can mess up things is changing the default language. This creates an inconsistency in translations table.

If you want to write javascript inside html body use the nonce attribute. The value of nonce can be retrieved from elxisDocument::getNonce() method (requires Elxis 5.6 or newer).

Example

<script nonce="<?php echo $eDoc->getNonce(); ?>">
    javascript code here
</script>

To check if you have Elxis 5.6:

if ($elxis->getVersion() >= 5.6) {
    ...
}

The nonce attribute tells the browser that this piece of inline code has not been injected to the content by third parties and it is safe to execute. The value of nonce is cryptographic secure and it changes on every click. Elxis put the nonce value on document headers when using a CSP policy.

... If CSP policy gets applied via Elxis configuration then all inline javascript, CSS and events stop working. This affects everything on the page, elxis build-in extensions, third-party extensions, html content from the editor, etc. This is why Elxis must be able to work under such strict security environment. If any problem arise then it will be on a third party extension (also require update).

It means that in Elxis configuration will exist the option to enable the CSP policy or not?

Inline javascript events get removed in order Elxis to work with strict CSP directives. Many files got modified for this purpose. Most probably not 100% of these events will be removed as they are too many. HTML and javascript get re-written. Even if some inline events get preserved these will not be of critical functionality and they will be removed on a later update.
Currently all frontend section and most of the backend has these inline events removed.

If CSP policy gets applied via Elxis configuration then all inline javascript, CSS and events stop working. This affects everything on the page, elxis build-in extensions, third-party extensions, html content from the editor, etc. This is why Elxis must be able to work under such strict security environment. If any problem arise then it will be on a third party extension (also require update).