Read manhwa Only I Can Speak the Ancient Language of Magic / 빙의했는데 고대 언어가 한국어였습니다

Waking up in a fantasy novel set in an ancient magical world was confusing enough for Sisha. But on top of that, she happens to be the only person who could read and understand the old texts recovered from the secret library kept hidden for thousands of years… Furthermore, to Sisha’s surprise, the ancient language of forbidden magic turned out to be none other than modern English! With the emperor now praising her ability to decipher the words of Alphabet, Sisha steps up from a mere sidekick to an incredible main lead–in a world where whatever she speaks in her mother tongue is a key to unlock the powerful magic.
https://teenmanhua.com/manga/only-i-can-speak-the-ancient-language-of-magic