5.1.9 translations are buggy.
try to update to 220.127.116.11 that should fix translation bug.
(for german it was ok after update, hope it is also ok for polish)
if fields are gone for edit content, look at top right inside options checkbox with acf-fieldgroup-name is maybe not ticked (there were you manage what is visible or not)
Welcome to the Advanced Custom Fields community forum.
Browse through ideas, snippets of code, questions and answers between fellow ACF users