Add a full stop after "humanity" and add a noun after "impressive". You can say: "I know a person who has done a lot for the progress of humanity. What is the most impressive achievement from this person?"

Up refers to the directions that are above. Down refers to the directions that are below. People use up and down when they refer to the direction that is straight ahead also. For example, "the bathroom is down the hall" means that it is straight down the hall. One can say that "the shop is down/up the street" and mean the same thing. Also, up usually refers to North and down refers to South, but most people don't take heed of that when they say "it's down/up the road". Two people who live in the same house could say "I live up Morse Street" or "I live down Morse Street". There are a lot of ways they can be interchanged. But of course, saying "up the stairs" is different from "down the stairs". Sometimes, they don't even refer to any direction at all. For example, "I live a few doors down from you". This doesn't mean they live below you or straight ahead, but somewhere to the left or right. The more you use them, the more you get the intuition for them.

Calaf iyo nasiib waxay ku saabsanyihiin qofka imaankiisa. Hal qof wuxuu dhihi karaa Illahay baa waaxaan ii qoray ama nasiib baan helay.

It means that he had an odd expression on his face. It's not funny in a humorous way, just in a weird way.

Sometimes a person gets certain discounts from their employer. When the employee can share his discounts with friends, it's called a "buddy pass". For example, if your friend works at the airport he might get free flights to give to a friend. This is called a buddy pass.

They are both okay. One is not better than the other.

That sentence is correct, but a lot of people wouldn't say it like that. There are many other ways to say it differently. I'll give you some examples: You don't know what you are talking about. You know nothing of what you speak. You speak of things of which you have no knowledge. Most people just say, "You don't know what you're talking about" because it's more casual or informal.