Hoon's answer is excellent. 마지막으로 does mean finally, but in englsh we have multiple ways of using that word; "for the last time" and "at long last". 마지막으로 means "for the last time", so what you said is actually "I have a kor/eng dictionary for the last time." in Hoon's example, he uses 드디어 instead, which means "at long last" or "finally!". Which is what you want to say. Perfect. Why "가지게 되었다"? Well, it literally means "it came to pass that I have it" or more directly "it became in a way that I have it". This is one way that Koreans commonly speak, or in other words, it's a cultural aspect of the Korean language. Verb게 되다 will always mean this and is most often used in past tense, even when describing a present situation. 한국에 오게 되었어요. "it came to pass that I came to Korea." And if you want to say specifically that you HAVE one rather than GOT one, his example is the best way I think. You could also say 얻게 되었어요 or 얻었어요. But i don't think you can just say 가지고 있어요 in this case.

나는 드디어 한영 영한 사전을 가지게 되었어요! finally 는 '마지막으로' 라기 보다는 '마침내'라고 해석하면 안 어색합니다. 제가 영어 문장을 잘못 해석한건 아닌지 걱정이 되긴 하는데요 "I have a Korean-Eng Eng-Kor dictionary!" "나는 한영 영한 사전을 가집니다!" is not correct but "나는 한영 영한 사전을 가지고 있어요!" Because "have" is not "가집니다" but "Take" is "가집니다" so "finally have" is not "마지막으로 가집니다" but "마침내 가졌습니다" 동태(action)를 나타내는 동사와 상태(state or condition)를 나타내는 동사에서의 혼돈(confuseing)입니다.(sorry, i don't know how to write in english) 이것은 한글과 영어 두 언어의 체계의 차이입니다. be + verbing --> "~ 하고 있다" i'm running --> 달리고 있다 i'm studing --> 공부하고 있다. but compare these.. i know --> 알고 있다. i remember --> 기억하고 있다. i have --> 가지고 있다. etc "I am knowing / I am liking / I'm believing / I'm remembering" is not exist in English, but we can use this word in korean "나는 알고 있다. 나는 좋아하고 있다. 나는 믿고 있다. 나는 기억하고 있다" these kinds of confusing happend to korean people a lot! I made a mistake also, i wanted to say "I'm looking for something" but i said "i'm finding something" there is no rule, you have to memorize it.. I also did when i learned english in my middle school sorry, this is all i can explain... there will be others who can help you 한가지 더 '되었다'를 사용한 이유는 상황(당신이 샀건 빌렸건 누구 한테 얻었건 그런 상황)이 당신에게 사전이 생기게 해준 것에 대한 수동적 의미일 뿐입니다.

I think it's wrong The sentence that "I finally got a Korean-English English-Korean dictionary!" means I want to get my dictionary, and eventually I get it So if you want to translate correctly in Korean 난 마침내 한영 영한 사전을 얻었어요!!