I don't understand why people say that they have not been taught something yet. I do believe that when I started this, I hadn't been taught anything yet. I started with 0 knowledge of German or its grammatical nuances. I am learning them through this program. When presented with new material, guess. It's going to provide you with the correct answer and its explanation afterward. You can also put in the extra effort and google it.
It was at the very bottom of the explanation of the word when it was first shown to us as a "new word." When you hover over the word it translates it and there is an "explain" box too. The explain box says it is careful or caution or respect.
What is happening here is that there are idioms in every language. In this case, the word for "respect" in German also translates in certain cases to "careful," just like how in English it is sometimes said as "Look out!" Taken literally, "look out" would mean to look outside, rather than look inside, but it is often used to mean be careful. Another way to look at is is that you are, or are needing to, respect the danger being posed, so thinking of it that way, it could make sense to use "Achtung!"
Not necessarily, there is a pattern to telling the gender of many nouns by looking at their endings. For example, you can be sure that most nouns that end in ''-ung'' or ''-tung'' are feminine e.g Belohnung is feminine. Just like you can tell nouns that end with ''-chen'' are neutral or nouns ending in ''-er'' are Masculine
There are tricks to learning some of them, but when I did German at school my teacher said that you pretty much have to just go with what sounds right. So if you say all three possibilities out loud, the one that seems to 'fit' better is usually right. I know it doesn't help much but once you start learning more it becomes a lot more noticeable.