Multiples Language Site with blog posts of both languages possible?

Hello,
I have a multiple language site (german/englisch) with english as default. I have some blog posts in german and english. The german posts have “.de” added in the file name.
So right now at the englisch page only english posts are shown and at the german page opnly posts in german language (posts with “.de” in filename).
But what I want is that in both cases all blog posts are shown, optionally with an extra tag like “[Englisch]” or “[German]”)

The current situation would be like this:

Englisch blog page:
How to plant a tree
Whats the best tree for winter?
list of biggest trees on earth

German blog page:
Einen Baum schneller wachsen lassen
Wie grün können Blätter werden?

And want I want:
How to plant a tree [English]
Einen Baum schneller wachsen lassen [German]
Whats the best tree for winter [English]?
list of biggest trees on earth [English]
Wie grün können Blätter werden? [German]

So all posts are shown in both languages, without copy pasting the content into a second file.
Is that possible?