Multilanguage site download issue

Hi to everyone,

I have a little issue with a download in a multilanguage website.
The front-end fetch always the same PDF even if in the txt everything is right.
This is the code and I really don’t know where I make a mistake

  <div class="section-fichier">
        <?php if($file = $project->file()): ?>
          ↳ <a href="<?= $file->url() ?>" target="_blank"><?= t('download') ?></a>
        <?php endif ?>


With that code you fetch the first file from the file system. Where do you define which file should be served? In a files field?

Thanks for your help, if I understand, in this way it take the first file in the folder not the one I put in the backend.
How I can fetch the right file I set in the backend?

My blueprint is made in this way:

            label: PDF joint à télécharger
            type: files
            empty: Selectionner le PDF
            multiple: false
            max: 1
<?php if($file = $project->download()->toFile()): ?>

Thank you very much