problems upgrading Jessie to Stretch

I upgraded Debain Jessie to Stretch, and cannot boot into the system anymore

i don't remember the exact procedure I used, but it went something like this:

apt-get update
apt-get upgrade

apt-list upgradeables ?

dpkg -c

change jessie to stretch in the /apt/etc/sources.list  sources

and reboot

i can get into recovery mode, but i'm not even sure where to start fixing it

any help is appreciated

thanks,

-dave.j