Weblate let you export and import translation file, even in CSV if it is convenient for
what you need to do.
I suggest not to make changes through pull request, because the added value of Weblate is
to notify translators, display a changelog, and enable reviews. The purpose is to lower
the requirements to contribute.
With a PR, as far as I know, these features disappeared, Weblate will silently update the
content. It will technically work, but it will prevent potential discussions between
translators.
--
Jean-Baptiste Holcroft