how can i download Adobe Illustrator cc 2020 on my macos big sur , 11.2?

Yes.. but adobe illustrator has changed.. no longer can you buy just Illustrator stand-alone.. and permanently... instead you must rent /pay to use /subscribe to Adobe’s Creative Suite of which Illustrator is a part ... monthly... . You can still rent/pay to use/subscribe to Adobe Illustrator itself, . .. they do have deals for teachers and students... .. but buying it is impossible.. you can only rent, period. And yes, you can stilll get it from Adobe.com

john b