Translation:The beginning is always more difficult than the end.
I said ' The beginning is always the more difficult than the end'. This is quite usual in English to insert the definite article before 'more difficult'. As Polish employs no definite article I considered the translation was sound but I was stupid to assume that Duo would be aware of this little bit of spoken/written English! I did report it.
Oh... just seen the bit about 'the ending'. Well, I accept the translation with thanks but I defer to the Br E explanation. One tries to be poetic in one's speech and 'ending' goes with 'beginning'. I am still intrigued to know about my previous post on 'the more difficult' rather than 'more difficult' in its context, of course.