They take only the english (US only I think, not sure) synopsis. I am surprised they took your es-ES runtime, must be quite a new improvement, amazing. I read somewhere they always choose the backdrop themselves, it has to "fit" their site design. Ask them about that directly.

Oh! Thank you. I'll do it. Very Kind :)

@avazqueg said:
Upload information from TMBD to Letterboxd
Hi! How are you?
I write you because I crated one page for one film in TMBD.
I write the sinopsis, and the tagline, and I put it too one image for the background.
But this three items didn't appear in Letterboxd.
What I have to do to upload this information from TMDB?

Here I link you the page on TMDB:
https://www.themoviedb.org/movie/1209635-ella-y-el?language=es
And here the page of Letterboxd:
https://letterboxd.com/film/ella-y-el/
Thank you so much.

Letterboxd uses TMDb API services.
Their information is that it can take 30 hours.
See below for a more detailed explanation if you are interested.

API - Update Delay
All data or images entered here on the TMDb Site are immediately available here on the Site.
Text data (titles, overview, cast etc...) in less than 1 second.
Images (poster, backdrop etc ...) take approximately 10 to 30 seconds.
It depends on the traffic at the moment.

But for a request made using the API, it will only be available within a maximum of 8 hours.
This period may vary depending on the flow of Requisitions.
Updates to TMDb Servers that are responsible for servicing API Requests are made periodically.
They are not done immediately.

In addition, in some cases, APPs or Services may also use the Cache feature.
The data may be available through an API Request to TMDb's servers,
but are not yet updated on the website or service, such as Letterboxd or Plex.
So, only when the website or service you use, update the information will you have the updates.

• If the problem is with Plex, you may be able to resolve it by reading the instructions on this link:
  https://support.plex.tv/articles/202967376-clearing-plugin-channel-agent-http-caches/

• The Addon for Kodi, TMDb Helper, according to the author has an Refresh Time of 24 hours.
  https://www.themoviedb.org/talk/5f9dbd98bc8abc003932c658
  https://forum.kodi.tv/showthread.php?tid=345847&pid=2874555#pid2874555

• Synology may be using Cache. It depends on how it was configured. Look here:
  https://www.synology.com/en-global/knowledgebase/DSM/help/ProxyServer/proxy_server_cache

• From Trakt.tv I still haven't found any official Cache usage information.
  Just a few comments.

• In the case of Letterboxd I do not know what is the frequency of update and/or duration of their Cache.
  Alias, if you get this information, post here the link to the Letterboxd page
  that contains this information about the Update Frequency and/or Cache Duration .
  EDIT: See here https://letterboxd.com/about/film-data/

  Changes to film data on TMDb will be visible in Letterboxd within 30 hours.