I have just bought a Lenovo Ideapad 330 and installed 18.04LTS. Turns out, touchpad is not working.

I found a solution for the touchpad here: [Lenovo IdeaPad 330 touchpad not working](https://askubuntu.com/questions/1049787/lenovo-ideapad-330-touchpad-not-working)
I then downloaded .deb packages for mainline kernel 4.19 and installed them. Touchpad now working (sort of).

However, I'm concerned about the warnings I got when installing the kernel, about about the kernel being unsigned and thus incompatible with Secure Boot. Also, when installing the package vim-gtk3 I got error messages about shim-signed and grub-efi-amd64-signed. 

Is there a way to get rid of these warnings/errors and still have a working touchpad? 

And what is this signed/unsigned business about anyway - why are some kernels not signed?