How to change existing document language speller?

I have a Writer document already written in Spanish, but I’m using English as my interface language, it was working fine, unfortunately my pc crashed and had to re-install it, when I tried to change the default English to Spanish for some documents, it won’t change, keep going back to English. What am I missing?
OS: MX Linux 21 (based on Debian 11)
LO: 7.0.4.2
ps: steps I took to change speller to Spanish => Tools > Options > Language Settings > Languages > Default language for Documents > selected Spanish > checked for the current document only
when I go back, still shows English, also the Tools > Spelling F7 is grayed out.

If Current document only is ticked, the language change will apply only to the current document. Others are unaffected.

To tell why this doesn’t work, more details about how your documents are formatted are necessary. The setting you changed is one of the most “generic” settings which can be overridden in many ways. In particular, if you have explicitly set the language in paragraph style Default Paragraph Style, this will override the “generic” setting.

Have you configured built-in styles to your needs? In which case, you must understand the interaction between generic settings in Tools>Options and styles.

Thanks for this tip, you’re right, I did create paragraph style, but I don’t recall if I explicitly set the language, I have 2 additional questions:

  1. is there a tutorial explaining how to create paragraph style (only paragraph style?) no language specific?
  2. in my case, how can I fix it? by removing the language in each paragraph style I created or there’s a more generic (that can be applied to all styles created) way to do it? Where in the style you can set the language? couldn’t find it.

The Writer Guide is a good introduction to styles.

If you don’t want your paragraph style to be linked with a specif language, don’t touch Language menu in the Font tab.
If you already changed the language, you must restore this setting to its transparent state so that it inherits from generic configuration. This is done by pressing button Reset to Parent in the Font tab. You may have to reconfigure font face, variant and size. The button may read Standard in 7.0.4.2 (I don’t remember when label change occurred).

Understood, thank you again for the tips.