I'd like to add something. Here in Russia, we don't map "утро", "день", "вечер" and "ночь" to exact time. "Утро" is generally time when you get up and kind of "tune into your day". "День" is when you're up and running smoothly, you don't feel sleepy and don't feel tired yet. "Вечер" is when your (work) day is close to its end. So, if you start working at 8, you are likely to perceive 10am as "день", but if you don't have to work and only get up at 12pm, this is definitely "утро" for you.
If someone is going to bed, you can say it to them, regardless of the time.
If you are going to bed, but other people aren't necessarily, you can say it if it's night.
If you are going to bed but it isn't yet night, you shouldn't say it unless other people are also going to bed.
Have I got it right now?
I'm not sure about that. If it is night, then I would say it if I'm going to bed, or someone else is, or perhaps even if we're just going our separate ways but nobody's going to bed yet. If someone, whether me or someone else, was going to bed during the day, I'm not sure what I would say. I don't think I would say "good night" except as a dismal attempt to be amusing. Perhaps "sleep well" or something like that.
This pronunciation is awful. It sounds like "Доброе" when it should be "Добрый"
Доброе = neuter
Добрый = masculine
Доброй is a different case, see here: https://en.wiktionary.org/wiki/%D0%B4%D0%BE%D0%B1%D1%80%D1%8B%D0%B9
I still don't understand why Добрый день can't be translated as "Hello" here. It's "Dobrý den" in Czech (so basically the same as in Russian). Where you would use "Dobrý den" in Czech, you would use the English "Hello". And as already some people mentioned, it can be used even in the morning (but not too early one). And I'd say that "Hello" is more used than "Good afternoon".