I studied Korean first, and now I'm learning Chinese. They're both very challenging, but in different ways. The Korean writing system and pronunciation are very easy, while the grammar is very difficult. I find Chinese grammar to be very easy (so far), while the writing system and pronunciation are incredibly hard. In fact I never really had any problem pronouncing foreign languages until I tried Chinese tones. So it really depends on what language you're learning.

A studio apartment is one level below a one bedroom apartment. A one bedroom apartment usually has a separate living room, but a studio has just one room for living and sleeping. There is also usually a kitchenette rather than a full kitchen.

Yahoo and MSN are not as popular in the US as they are in other countries. In fact, I had never used MSN, and didn't even know it still existed, until I started talking to people abroad. AIM (AOL Instant Messenger) is actually pretty popular, even though AOL is not. A lot of people talk on Skype and other services, and I mostly use Facebook chat to talk to people.

To write in English is difficult That one sounds awkward. It's probably considered correct, but it sounds strange. Also, "I use to make mistakes" should be "I used to make mistakes." But that is a mistake a lot of native English speakers make too.

Usually it means "therefore" or "so." Like, (어떤 사람이) 저기 앉아요. 그래서 담배를 피워요. So maybe, that person is sitting there, so he is smoking a cigarette. Or, that person is sitting there and smoking a cigarette.

The meaning is the same. If there's a connotation difference, I haven't been able to tell