The sentence I highlight, how this is not generate by my content. 

How can I change the word of the sentences in the "Prefer to stop receiving these emails? Unsubscribe here." 

 

You will want to edit your language pack.  

ACP > Customization > Localization > Languages

Click on "Translate".  The phrase "Prefer to stop receiving these emails?" is unsubscribe_blurb and "Unsubscribe here" is unsubscribe.  Search for those keys and replace with what you want.  You can also just search for the phrase instead of the key as well.