Consequences of website translation into another language

[Arhel]

Good morning everyone.
There is a website with good results, etc. In terms of optimization, there are few questions, but .. Recently the customer wanted to completely translate the site into another language (Spanish), because now it is in English. How does this translation threaten Google indexing and how to properly minimize traffic losses? (currently, up to 7000 people per day).

 

[Seldsang]

In the same place, some wild law will soon come into force that the main page should be in English by default. And then the user can choose the language.