Translation:The girl is nice.
착하다 • (chakhada) (infinitive 착해 or 착하여, sequential 착하니): (to be) goodnatured
좋아하다 • (joahada) (infinitive 좋아해 or 좋아하여, sequential 좋아하니): to like something or someone; to prefer
좋다 • (jota) (infinitive 좋아, sequential 좋으니): to be good; great; excellent (Excellent and satisfactory in features and content.) good; nice (Well-rounded and kind in personality.) good; kind (Kind and gentle in the way one speaks and acts.) good (Above average in physical condition or health.) having a lot of nerve (Not caring about saving face or being shameless.) nice (Sunny and clear.) enough; sufficient (Enough or sufficient.)
작은 • (jageun) (determinative form of 작다): small
작다 • (jakda) (infinitive 작아, sequential 작으니): (to be) small
이 and 가 are the same and mark the subject* of the sentence, while 이 is used if the word on a consonant. Otherwise (for vowels) 가 is used.
을 and 를 mark objects**
은 (vowel) and 는 (consonant) mark a new topic*** and are used instead of the other particles.
- subject = something or someone that does something object = something or someone that something is some to * topic = a new topic in a conversation. in English you could roughly translate "... 는" into "concerning ..." or "about ..."