In Australia "My Father is going well", or just "My Father is well" would be the preferred translation. Phrases with "doing" are very American, and sound incorrect to our ear - in the same way that I am guessing "going" sounds to you. I have a Canadian friend who always laughs when visiting Australia, he gets asked "How are you going?"
It is correct English, depending where you are from. Perfectly acceptable and grammatically correct. There are many correct Englishes; hard to write algorithms that catch them all. As human beings we need to be more open to accepting that there is no "one" correct, or even "standard" English. It all comes down to where you're from (and/or where you learnt your English).
It isn't! It is just that we are sometimes baffled because there are faux Amis words between US and UK English, other English speaking countries, areas and regions. A US yard here is ordinarily a (UK) garden. Pants here are underwear not jeans or trousers, etc. So, we are all learning varieties of English, too. It can be fun. Are you wearing your red pants? would be a very personal question in the UK! Just bear with us whilst we learn American!
I listened, listened and listened to what the voice was saying and I still say it was saying frere and not pere. This has happened several times in other lessons causing my answers to be shown as incorrect. Is there any official, supervisor, advisor, moderator or anyone else in authority at Duolingo who can discuss this problem with a student with a view to trying to correct it?