I am pretty new to Illustrator and for my job I am updating ai menu files and uploading them to Google Drive. Yesterday someone told me I needed to make the file size smaller so I found a Youtube tutorial on how to optimize the file size. It made the file size smaller, but once I updated the file into Google Drive the colors where completely screwed up and some of the colored text was missing. When I open the file it looks fine, but I've never had this issue before I tried optimizing the file so I think I may have messed something up. I have attached images for reference!
What did you do to your file?
And if the file in Illustrator is OK, then why care about how Google shows it?
If you prepared the file for print, it has a CMYK color mode. It's OK for this mode to be shown incorrectly in usual viewers like Google, Explorer, etc.
If you save as a PDFx4 you will get a smaller file that is good for print, you will lose your illustrator editability, but the visual appearance of your file will be as it should. The reason your file is big is to keep editability, so you will be throwing away some information that makes but not anything that affects the appearance (you will want to keep the full size file for editing)