LibreDictSupport
Write to support@libredict.app or on Telegram. In the app you can also report a bug: Settings → Support → Report a Bug.
Questions and answers
Do I need internet?
English is included. Every other language downloads once, when you choose it, and then works offline.
Where are my old bookmarks?
In My words, in the Learn tab, once you have chosen a language to learn. They are the same words.
How do I download or remove a language?
Settings → Dictionaries → Languages.