And добрый ≠ good (because «добрый» usually means 'kind' and not 'good'). However, in the context of this sentence this works as a translation. :)
Russian nouns have one of three genders assigned to them: masculine, feminine and neuter. Ве́чер 'evening' is masculine, у́тро is neuter. Most feminine nouns end in -а, -я or -ь; most masculine nouns end in a consonant or -ь (sometimes in -а or -я); most neuter nouns end in -о or -е.
The adjectives should have the same gender as the noun: до́брый should be used with masculine nouns, до́брая — with feminine, до́брое — with neuter.
Since unstressed vowels are reduced in pronunciation, both до́брая and до́брое are pronounced in the same way, /'dobrəjɪ/. But the difference exists in writing. To understand which one you should use, look at the noun. If it's feminine, you use до́брая. If it's neuter, you use до́брое.
In English, I would use "Have a good day" as a farewell phrase. But in Russian, «Добрый день» is a greeting, and «Хорошего дня» is a farewell phrase.
In the Lonely Planet Russian phrasebook from March 2006 on page 111 Добрый день is shown to mean good morning/day, exactly like that with the "/" between morning & day. I think it's like good morning in spanish, buenos días which literally means good days, but is understood like good morning is understood in English.
It can refer either to
- the part of the 24-hour period when the sun shines (in fact, «све́тлое вре́мя су́ток» 'bright time of the 24-hour period' is a cliché phrase in Russian, used instead of «день» sometimes), or to
- the time between after «утро» 'morning' and before «ве́чер» 'evening' (='afternoon'), or
- sometimes it can be used instead of «су́тки» to refer to '24-hour period', especially in colloquial speech where «су́тки» sounds too formal.
Most Russian consonants have two variants: soft and hard. So, н has two variants: hard н and soft нь. This is similar to Portuguese n and nh, but this difference exists for most consonants in Russian, not just for n/nh and l/lh.
Before vowels, the vowel sign marks the softness of the previous consonants (а, э, о, ы, у is used after hard consonants: на is hard н + а; я, е, ё, и, ю are used after soft consonants: ня is soft n + a). In other cases, softness is marked by soft sign (нь = soft н). Hardness is unmarked, it is assumed by default (this was different before 1917: back then, Тим would have been written Тимъ).
To make things more complicated, я, е, ё, ю have double meaning. After consontant, they show softness of consonant and mark a vowel sound. But after vowels, at the beginning of the word, and after ь and ъ, they mark Y sound + vowel sound. I.e. я = йа, е = йэ, ё = йо, ю = йу. This is the only case when ъ is used in modern Russian: in подъезд, it shows the pronunciation под-йэзд (with hard д, Y sound, and then e).
You can search forum discussions for soft consonants, they cause difficulties for many learners so there should be many questions related to them.
It seems the software is very liberal on Russian spelling. I often get things correct without any warning of a typo(using Google Chrome browser on MacBook) only to see a different but similar spelling to what I answered(e.g. добрий ден тим) in the discussion. I know Spanish, French and Italian on Duolingo are pretty consistent on notifying about typos even down to the accents. Is this liberalism in spelling also true in the actual written Russian language, or is it just on Duo to account for people using the Latin alphabet to answer? If it's the latter, could there please be typo messaging added even though it's counted correct. I want to be able to spell correctly without double checking the discussion every time.