Questions about the Tantei Gakuen Q manga?

-I recently finished watching the anime series (which had a total cliffhanger for an ending) so I decided to read the manga. I checked online and the I learned that the manga series finished years ago. But then, in many different online manga reading websites, they only posted until volume 7 (in english) but there are more than 20 volumes all in all. I'm just wondering why there aren't more chapters posted. Is it because it takes longer to post in English? Thank you!