As a native speaker of Korean it has been quite easy to learn Japanese, as the word order and the way of expressing things are extremely similar for the two languages.
The languages are resemble each other so much that substituting each word and grammar particles usually makes sense as a translation. The nominative case marker usage differs more frequently than others but even that difference is small enough that Korean sentences using Japanese case marker style is understandable by a speaker of Korean. For an example let me explain the differences in English, Korean, and Japanese in example sentences in each language that means the same thing.
English also has the verb "am" which, in English, is required for an adjective (predicate adjective it is called in this case) to modify the subject of a sentence. This is very different from both Korean and Japanese, both of which treat adjectives kind of like verbs (it is possible for Japanese and Korean and adjective to conjugate to reflect the tense, aspect, mood, respect levels, etc. without the help of a linking verb like "be", "am", etc.).
English is very different, again, as it uses a prepositional phrase (no prepositional or postpositional phrase is used in either Korean or Japanese sentences) in order to describe what the subject "I" is good at.
It is interesting how the most important information in the English sentence ("English") is in a grammatically unimportant position. By this I mean that the word "English" is neither the subject nor the object of the sentence. It is merely the object of the preposition "at" which modifies the predicate adjective "good" which in turn modifies the subject "I" with the mandatory help of the copula (linking verb).
This is my best attempt and it is really bad because English lacks the topicalization marker (은 or 는 in Korean and は(read as 'wa' when this is a topicalization marker) in Japanese). English also lacks the object marker and even the accusative case is only prersonal pronouns such as "me", "thee", "them", "him", "us", and "her". The 를 in bold is the accusative case marker in Korean and this differs from Japanese because in the Japanese sentence the bold text is actually the nominative case marker which marks the subject of the sentence. This is one difference between Korean and Japanese. Finally, English lacks the verbal ending ("ㅂ니다" in Korean and "です” in Japanese) that marks respect toward the listener.
So the Korean sentence is organized in this way: the "subject" of the sentence is marked with 는 which is actually a topicalization marker. The word 나 (first person singular informal) is actually not a subject but a topic, which is quite hard to explain but topic is usually less important information wise than subject in a typical sentence. After the topic+topic marker pair, the object 영어 ("English") and the accusative marker 를 comes. Finally the verb at the end to fit in the SOV order ends the sentence. The verb has quite some parts to it. The whole verb is "잘합니다" with three parts: "잘" + "하" + "ㅂ니다". "잘" means "well" and can be interpreted as a adverb. "하" is a verbal stem which means "to do" and it actually cannot be used as is because it verbal stems require verbal ending in Korean. "ㅂ니다" is the verbal ending that shows respect toward the listener. This gives a polite nuance to the listener. Since there is no past tense marker, the sentence is in the present or in the indicative mood. The verb can actually be "well does", but the verb is a very common one and it usually is used together so much that it became a verb (or I should say "adjectival verb").