@DaniDee @Chun Mo Rionnag
I also started with "Talk to Me in Korean" textbooks, and also
"KOREAN PRONUNCIATION GUIDE"
Editorial : DARAKWON - Author : Kim Jimin, Yoon Shinae, Lee Eunju
In that book you will learn how to pronounce shapping the tongue, lips and all the mouth.
And also pronounciation rules such as aspirated consonants, fortis, palatalization, nasalization...
For example:
Nasalization when the next syllable beggins with ㄴ or ㅁ
Syllable ends with ㅂ, ㅍ → [ㅁ]
Syllable ends with ㄷ, ㅌ, ㅅ, ㅆ, ㅈ, ㅊ, ㅎ→ [ㄴ]
Syllable ends with ㄱ, ㅋ, ㄲ → [ㅇ]
is written 입니다 → is pronounced 임니다
is written 닫는 → is pronounced 단는
is written 국물 → is pronounced 궁물
You can also learn why (you hear) koreans say "doona" 두나 instead of "noona" 누나 or.. when they say (yes) 네 you can hear /De/
Because the position of the tongue in the "N" (in english) is touching the tip, while in Korean they touch with the blade of the tongue, that's why ㄴ /n/ seems like ㄷ/d/ and also by the position of the lips and tongue why ㅁ/m/ seems like ㅂ /b/ like in (What) 뭐 -> 붜
NOTE: This only happens when the word starts with ㄴor ㅁ, the rest of the syllables are pronounced normally.
I also recommend the Naver KO-EN Dicctionary
You have a Wordbook where you can save vocabulary from TOPIK and mark as mastered those words you already know or learned. But I think you need a naver account in order to save the progress.