is there any way to download a full manhwa or manga?

I don't think you'll be able to download full here in mgg unless you individually dl the pictures one by one but I think you'll be able to if you download tach*yomi then select mgg as the host for the reader ╮(￣▽￣)╭

Unfortunately you'd have to save every image, but if you have an andriod there's an easy way to save every image on a page at once, that's what I did once

Maybe download the whole chapter as a pdf?