I have a running website of with some hundreds of thousands of pages already indexed, let's say example.com
Website needs to be translated to some other languages with the purpose of getting more indexed and get more traffic.
If I create example.com (default, for English), es.example.com, de.example.com...
The already indexed pages will remain and the other ones will be added, right?
In the other hand, if I redo all the link structure of my page creating
example.com/en/user
example.com/en/settings
example.com/es/user
example.com/es/settings
example.com/de/user
example.com/de/settings
I will lose all the indexed pages (or at least will need to be reindexed) and it takes way more effort from my point of view. Current indexation example that could be lost with change:
example.com/user
example.com/settings
Which is the best solution regarding SEO and indexation?
PS: I already read other questions like this one and understand the benefits/issues of both solutions, the difference here is that mine is a running website with some thousands of visits per day that can't be lost.
EDIT
I also read this and understand everything, but still don't know for not losing my current indexation