I've finished three days of koine Greek, which is equal to three weeks of Greek in a normal semester. Now it's getting hard. Greek is a fully-inflected language, which means they change the endings of both nouns and verbs in order to show things like the case, gender, and number. So for example, the verb "lego" means "I say," but it changes to "legomen" to mean "we say." You have to memorize all those endings. Similarly, the noun "ha doulos" is "the servant" if it's the subject of the sentence (e.g., The servant pokes.), but it changes to "ton doulon" if it's the direct object (e.g., I poke the servant). If you change that to the plural (e.g., I poke the servants), it changes again to "tous doulous." You have to memorize all those endings as well. Of course, it's actually much harder than this. I gave you the transliterated version (Roman alphabet); we have to learn it all using the Greek alphabet with all sorts of extra funny marks to denote things like accents and breathing marks.
Sample Greek lesson
Learning Greek's not impossible, but it certainly is hard work. But I'm really enjoying it. This will allow me to studying the New Testament in the original languages, something that's very important for pastors to be able to do. One job of the pastor (literally shepherd in the Greek) is to protect the flock from doctrinal errors; to do that well, you have to know the original language the Bible was written in.