Manga doesn’t automatically get an anime if it’s popular. It depends on if an anime company wants to make an offer or not, and whether that offer is accepted. It’s totally possible for a non-native mangaka if they are good enough. I use photoshop, illustrator, Manga Studio, and Indesign when I’m doing artwork. Sorry, I don’t know who is looking for assistants.. you’re free to check for yourself, though!