Did you link the correct page...? This one is just four brush strokes, lol. It should take a minute max. So I don't belive it took you an hour and a half.
So? Here is the page - I challenge you to remove the Chinese watermarks in under a minute, then post it. Or stop the snark. It took 90 minutes to clean, redraw and shade in the image. http://www.mangago.zone/read-manga/you_re_my_loveprize_in_viewfinder/mh/manga/you_re_my_loveprize_in_viewfinder/v09/c055/pg-13/
And I have a degree in Graphic Design and Fine Arts
Are you doing it on purpose?
Someone (don't recall who) said, rather arrogantly, that they could clean and redraw the whole chapter in 20 minutes. Well, I just spent an hour and a half cleaning this page - just for shits and giggles, and I challenge whoever it was to try the same, and do it much faster http://www.mangago.zone/home/photo/1532693/
I have a crappy program to do this in, but I know how much time it takes to clean and redraw.