Good job,... I am not sure on that (how to install the one at "git hub"), I saw it as well, If it was me, I would try these first:
https://wiki.debian.org/SynapticsTouchpad
Debian 9 "Stretch"
In most cases, make sure you have the xserver-xorg-input-libinput package installed, and not the xserver-xorg-input-synaptics package.
If the packages in the Debian repositories do not work, then the git hub, one
would be a last resort. You will need to learn how to compile it, to install,..
I am not that advanced, but maybe someone else here can and will go into
details on that.
P.S. I don't think trying to use Debian Buster (testing) would be a good
idea for you.
------------ slightly off topic----
As far as installing from Github, there is a 'make' file, so you could do some
more searches, on "how to compile and install a driver using make, and make install" Hint:(include "for Debian" , in the search key words, will narrow it down more) . Recently I just started learning a little on this, but it is not Debian or Linux, been compiling and installing some programs for Minix 3, using , make, make install, and also cmake, and bmake,... however what works for me on
Minix, did not work for me on Debian, not surprising though, Minix is not even Linux, so any way I don't have the experience, knowledge to help on that, sorry.
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P.s. Not a solution but a work around, so you can use the laptop, If you have a
USB mouse, have you tried that ? It should work.I do not like touch pads at all,
and have found that even when the touch pad does not even work, a usb mouse does, I all ways keep one in my "case " for my laptop, when I travel.
Need to try google translate, not sure on the english word....edit :ah ha
Not case , "brief case", or "back pack"