Kernel Panic

OK, that sounds like progress, right? It’s booting now without selecting the older kernel?

I’m pretty sure that Ubuntu will automatically update the kernel unless you specifically tell it not to. When you ran the updater again just now, it may have self-corrected the problem it was having. It is probably best to just let that regular update happen unless you continue to run into problems.

But, these terminal commands should update the kernel if needed:

sudo apt-get update
sudo apt-get dist-upgrade

If you are willing to install a special app for kernel updates, this page looks interesting.

About crashing and running slow (not counting slow internet connections)… I don’t find Linux to suffer from those system slow-downs nearly as much as Windows, but I would probably take the same approach: it might be time to re-install from scratch. But before that, you might be sure to disable some or all browser “plugins” or “add-ons” that you may have… those can also cause trouble sometimes. There are some other things too if you see serious slow-downs… the top command can show you the running processes that are using the most resources, and you might identify a problem app that you could uninstall. But it can be quite a challenge sometimes to find slow-down issues.