I'll take on one more of your phrases (because it has a humorous personal story with it). For "I don't know" or "I don't understand," the dictionary form of the most common verb used is 모르다 (moruda). The usage requires a bit of understanding of levels of respect, and how tense and endings are used to add some shade of softness or meaning to the expression. In base form, if someone says something and 1) you don't have any knowledge of what they are talking about, or 2) you understand nothing, I think this is where I would normally hear 몰라요. (mollayo. The stems changes to double the ㄹ and makes it into a strong ll sound for this verb ending). If you know about something, but you're not sure of the answer, or not sure you would get it, you might use 잘 모르겠어요 (chal morngesseyo. The "r" sounds like a Spanish 'r' in this case). The shade of meaning on that is more like "I'm not sure," or literally "I don't understand well." If you're telling someone you don't speak Korean well, then you would more likely say "한국어 잘 못 해요" (Hangugeo jal mot hae-yo). The meaning is more like "I can't speak Korean well" (and using "못" this way, you imply that you WANT to, but haven't been able to.) The quick story: When my wife and I first met and became friends, her English was weak, and my Korean was non-existent. As we spoke sometimes, I noticed she would sometimes answer with "몰라." So I asked, "몰라, what does that mean?" She answered, "I don't know." I got confused and asked back, "What do you mean you don't know. I hear you say it all the time. What does it mean?" "I don't know." "But you just said it, and you were answering me!" It took a few exchanges before she was able to finally get it through to me that 몰라/몰라요 (molla/mollayo) actually meant "I don't understand" or "I don't know." :) That little story is one of our kids favorite stories - our own little "Who's on first?" moment. :)

Most of these are not simple, 1:1 translations. This is an area where a person has to begin to detach from thinking in English when going to Korean. Let me take on a few of these, but I can't do all of them. I may use more than one answer. And: A few words that translate to "and" include 그리고 (keurigo), 와 (wa), 과 (goa), 하고, (hago), or just using the verb ending 고 (go). 도 could also be translated as "and" in some contexts. Examples (non-exhaustive) of using this include: To connect two nouns in the subject, you would use 와 or 과. If the first noun ends in a consonant, you would use 과, and if it ends in a vowel, you would use 와. Actually a good example of this is the popular cartoon "Tom and Jerry" which ran as Tom 과 Jerry (Mixing Roman and Hangeul). However, detach yourself from English thinking as sometimes the conjunction follows the noun joined in Korean. A couple of examples: When "I" is understood as the subject, if I'm going to the convenience store downstairs along with 준혁, I might tell my wife that 준혁 is going with me by saying "준혁과 같이 편의점에 갔다 와요." (Joon-Hyuk goa gatchi pyeon-i-chemo gatta wa-yo) (Wow! It's hard for me to type Romanized Korean - my fingers keep finding where the Korean letters should be :) ). Use 하고, or the verb ending 고 at the end of a verb when connecting two clauses in a sentence. If you finish a sentence and need to start the next sentence with "and," (something that is improper in English, but is done in Korean), you start the next sentence with 그리고. I'm probably out of characters in this reply. I'm trying to seriously answer the question, but in answering, I need to demonstrate that most of these do not have straight 1:1 translations, but rather, have grammar principles you also need to understand in using them, and they need you to begin to detach your thinking from your first language, and learn the usage in Korean.

I answered 2. In particular "I guess" is a big topic as there are several ways to express uncertainty in different contexts in Korean. Those ways are used in everyday conversation, too. In level 2 of Seogang's Korean, there are at least two chapters dedicated to 추측 (choo-chuk) which is a guess. 추측 means "guess," but you don't use that word in a sentence like you do in English. You may have to give us examples of what you want to say so we can begin to explain how to use it. several others, such as "well" and "great" in particular, you need to give us examples so we know which definition in English we need to translate into Korean. I'll leave some for other people to pick up, and of course, invite them to comment on what I left as answers.