Hi and welcome to the forum! Please note that this is an English-speaking forum, and so you must speak in English, or at least provide an accurate translation of what you wrote. Since you didn’t do that I’m gonna translate it for you:
In reply to this:
I’m sure to answer: no, you can’t change PHP version on free hosting. There is already a PHP upgrade to PHP 8.1 in the way, but it’ll be rolled out once iFastNet gets missing PHP extensions back to that PHP version. You might be better off downgrading the dependencies’ versions so that they are compatible with PHP 7.4 though, or even better downgrade the version of the software that requires Composer you’re using to a version that is still compatible with PHP 7.4 for now, or if you still need the latest version of the dependencies, either wait for the PHP rollout on all hosting accounts or upgrade to Premium Hosting as there you’ll also have PHP 8, a version selector for PHP, and more features than on free hosting.