Text language for regions

I want write a multilingual text, for example:

Hello, this is a tree
Hola, esto es un árbol
Bonjour, c’est un arbre
(*) here is my cursor and i want write the same in german

The specific question is: How i can specify that the next on the text is in german?
I know the trick that write and wait for the dictionary suggest german, but sometimes simply dont work or sugest “this word is in german / This paragraph is esperanto” and change word by word is not busines because the real text is not only 4 words
So i want some like bold, or underline “activate XX language” and deactivate and back to the document language.
Best Regards for everyone

In addition to the answers, read this tutorial.

You need to use styles for that: with both, character styles (for short fragments of text) and paragraph styles, you can define the language in the Font tab. Then, apply the styles as needed to change language.

Note that you can assign keyboard shortcuts to styles or create a new toolbar with individual buttons for each style. Always remember to apply the “default” style to return to the main document formatting!

Simply switch your input language to German, Esperanto etc. LibreOffice will understand it. Styles are excellent, but when your text is truly multilingual creating a separate style for every language may be too time-consuming.

Please note tdf#108151, which suggests that on Linux, system input language is ignored (and I actually see that on my Ubuntu 18.04). @gabix: you mentioned elsewhere that it works for you on some flavor of Linux; could you please provide relevant info to the bug?