"A man is eating a fish and soup."
Translation:Mężczyzna je rybę i zupę.
Polite forms: Pan/Pani/Państwo are commonly used and using them is not considered childish
at all. Actually, not using them when you address unknown, elderly people, or public officials, is considered... rude. To start a conversation:
Excuse me Sir... - Przepraszam Pana...
Excuse me Madam... - Przepraszam Panią...
Can I ask you a question? - Mogę Pana/Panią
o coś zapytać?
Sir/Madam, can I help you? - Proszę Pana, mogę Panu pomóc?/ Proszę Pani, mogę Pani pomóc?
I would even agree that with eating, the "fish" = "fish meat" interpretation should win, but as it's already problematic to teach "ryba/ryby" when both are translated to "fish", I think it's lesser evil to keep "a fish" as "one animal" here.
After all, there is also a sentence "These people eat ducks", and it's not exactly about eating the meat. Far from perfect, but...