Saving edited pdfs directly to Gdrive doesn’t work

this has happened to me several times. I download a pdf file from my online student forum using Safari, start editing it I markdown ( taking notes during lecture etc.) and then, at the end of the lecture, want to save it. I choose „ done“ — „save“ and as a location I choose Gdrive. But it immediately appears with a little red minus sign, and later when I want to open it from Gdrive into Acrobat, it sails there is an unknown error and to try again later. When I click the file once, it shows the thumbnail/preview with my notes, but it cannot open them… this is quite unnerving and affects my academic performance.

I have tried to wait and see if this is an issue with internet connectivity, if it will upload later, but this hasn’t been successful. The files are around 10-20 MB, and the speed of my university internet is around 5Mb/s, so an upload shouldn’t take much longer than 30 sec anyways.

any ideas/ suggestions ? Atm my only workaround is to save the file locally and then upload later..