If other languages are not defined show english Is it possible to get the english content on the, for example, Spanish site if the Text for the specific language is not defined yet?

I do not mean a redirect! The English version should be displayed until the Spanish content has been inserted. 

It would be great if someone has a Idea! Thanks!
You could choose which value to translate your content into using the |t($lang) filter based on some condition. You condition could be a lightswitch field on each entry saying whether it's been translated or not, or check if a content field is empty or not.

So something like

set lang = entry.lang

if entry.isTranslated == false {
   set lang = 'english'
}

{{ content|t(lang) }}