Translation:It's not six o'clock now.
Learning words like this is not flawless. There are some words whose readings may change depending on context. For example, 何 (なに) can be read as 何 (なん), and 一 (いち) and 分 (ふん) together are read as 一分 (いっぷん), but clicking the kanji individually will not teach these alternate readings.
When you click on the Kanji sometimes It doesn't play the same sound, because Kanji makes multiple different sounds. So clicking everything individually may not always work. But sometimes In other lessons they provide a turtle mode. That is when learners learn to recognize a sentence character by character. But in this case, there is no turtle and it's not slow because it is teaching the learner to recognize a sentence as a whole. Like if they were in a conversation, there is no turtle mode on a person.
You're probably not wrong. There is no particular logic to when DuoLingo presents new grammar and vocabulary. It's basically random.
In this case, は marks 今 as the subject of the sentance. 今 means "now" or "right now".
So a literal translation of this sentance would be something like "As for right now, it is not 6 o'clock."
It sounds like "rokuji", because of the time marker 時 (ji). There is no pause between roku and ji when saying the time - it flows together like one word.
Listen for the first は and it will come right after it and before the では. Here is the romaji version to make it easier to pick-out what you are listening for in the audio.
"Ima wa rokuji dewa arimasen"
IMO, "It's not six o'clock" by itself in English is colloquially equivalent to "It's not six o'clock now", because the 'now' is so often assumed when speaking about time. When English speakers refer explicitly to the time they'll say "now" (or even "right now"), but if a sentence is just a statement that it "is" a time, it's presumed IME to be the current moment in particular.
One question: For anyone that knows, why is it ではありません instead of じゃない for the negative "to be", simply put "isn't"? ある means "have", so logically ありません is "haven't/hasn't/don't have/doesn't have". Do we say "it doesn't have so and so hour" in Japanese? Or is verb conjugation in and of itself different than what I have in mind?
In Japanese we say "A state XXX does not exist" to mean "It is not XXX." This is exactly で(as a state/concept)は(stressing the negative)ありません(does not exist).
じゃ is a euphonic change of では (では dewa => diya => ぢゃ => じゃ)
ない is the negative form of ある
So じゃない is a verbal informal version of ではありません.