Most people will predominantly translate between their native language and one or very few languages.
Recently used languages should always display first, in chronological order, followed by a break, followed by the *full* alphabetical list of languages (ie don't move the recent language to the top - display recent first, then the full alphabetical list so that there is no instance where a language is difficult to find).
Scrolling full list every time is one of several tiresome design choices that don't adhere to UX norms.