Translation:Ano, dobrý den.
Yes, I would agree with you. If it wasn't for the fact that you give Hello as a default translation for both in other sentences. That is Dobrý den and Dobrý večer. It's the inconsistency of it, that I don't like. And if you accept it in one direction, it should go both ways. Or, you should remove Hello as a translation for Dobrý den and dobrý večer.
Dobry is masculine, dobre is neuter, changes according to the noun it's in front of. Dobra is feminine. Not sure if that last one (dobrou) is a form or not, I'm not that far yet XD
If someone else could answer though that would help both of us :) I looked it up on google translate and it said "good night" for some reason
Essentially, you need to memorize/absorb declension tables, which indicate how the form of a word differs based on its use. In the case of adjectives, their form differs based on the gender, number, and case of the nouns that they modify. The chart at the link that follows will give you an idea of how dobrý changes, and you can look up pretty much any word there as well: https://en.wiktionary.org/wiki/dobr%C3%BD. It can be confusing at first, but repeated practice of the lessons here will definitely help.
With your friends or relatives or other people that you can call "ty" instead of "vy" ( https://en.wikipedia.org/wiki/T%E2%80%93V_distinction )
Or "ahoj" universally when on a boat, kayaking or canoing or something similar.
Of course, Good afternoon and Good morning are more formal. But they are not universal so they are not a good choice here. We had too many people complaining. But seeing your complaint, one cannot satisfy everyone
In the UK strangers would often just greet me Hi mate or Hello luv although they were at work and I was their customer. Hello was aceptable everywhere in my daily live, but I did not join any business meetings.