I have this issue with my dual boot laptop (Win10 and Ubuntu 18.04):
I logged in Ubuntu, initially, without a huge issue, and was trying to download a file via Chrome, which failed due to a full disk error. Foolishly, I replied to this by rebooting the system and then all hell broke loose, as my computer couldn't boot into Ubuntu, constantly displaying a black screen with information on the boot process and being stuck on "Started hold until boot process finishes up". This, according to the internet, means my disk is indeed very full, which lead me to running Ubuntu recovery mode, selecting "clear" in an attempt to free up space, which didn't automatically free up anything. Next, I booted recovery > root and uninstalled a few packages I didn't need. After rebooting normally, I was prompted to enter my password on the Ubuntu Login UI, which I did successfully but my computer kept me logged out, again asking for the password.
I'm stuck, what do I do? Is there a safe way to add space to my linux partition through windows without destroying everything? Thank you.