In whatever browser you use (like Firefox or Chromium or Chrome or whatever) make sure to clear the cache. In Firefox, it's found at History/Clear Recent History... <-- this gives the option to clear all your history (you may wish to preserve cookies and logins, but the cache should be cleared.)

Also, run the following commands in your terminal/console:

Note, if these commands do not work, then try what's below. The commands above are the newer updated commands in Ubuntu, though maybe Mint still uses the older "apt-get" command. If so, try what's below:

This should free up some space. Some of the other suggestions made before by those with more knowledge than I are likely also helpful. Good luck.

It's worth running the autoclean command every month or two or after you've performed a major update to your system.

I tend to take a more manual method.

# dpkg -l | grep -v ^ii

# dpkg --purge --force-all <the packages no longer fully installed>

Until the list is short or gone, then:

# deborphan

Then remove the things not a kernel or bootloader. And of course:

# rm -rf /var/cache/apt/archives/*.*deb

But I'm normally on debian stable which doesn't have many updates beyond security updates. So not something that I do, except at the end of a fresh install, or every six or more months of running a distro. Although I tend towards quarterly fresh installs these days. In a post Snowden world. Plus a lot of times a fresh install is lower bandwidth than an update.