Emptying trash issue
I was looking for how to empty trash when it is "being used by another task" and what somehow helped was this:
1) Open Terminal
2) Type in "killall Finder" and press Enter - NOTE: all your Desktop apps and Finder windows will disappear for ~15 seconds.
3) Once everything returns, check Trash again - for me, it was emptied.
I don't know the logic behind this so maybe it was just a coincidence, but if you have a similar issue, you can try it out.