Manga are usually made by a team effort. A mangaka comes up with the story and does the initial sketches. Then, assistants help with inking, coloring, and adding backgrounds.
Manga is usually created by a mangaka who comes up with the story and does the illustrations. They start with a concept, draft the characters and plot, and then do detailed sketches and inking.
The Made in Abyss manga is on hiatus for now. Maybe the author needs time to flesh out the story or there could be other behind-the-scenes factors affecting the schedule.
Yes, it's possible. In America, there are artists and creators who have the skills and resources to produce manga. It might have a different style or flavor compared to traditional Japanese manga, but the art form can definitely be practiced there.
It depends. Some manga artists prefer to create everything digitally, using software and graphics tablets. Others still rely on traditional methods like pen and paper, and then scan and edit their work digitally for publication. So, it varies from artist to artist.