To start, login wherever you can, open YaST and ensure automatic login is not enabled. If you found it enabled, disable it, then reboot.
After waiting long enough for the login GUI to appear, do Ctrl-Alt-F1. Then after a pause of 3+ seconds, do Ctrl-Alt-F2 pause, Ctrl-Alt-F3 pause, Ctrl-Alt-F4 pause, Ctrl-Alt-F5 pause, Ctrl-Alt-F6 pause, Ctrl-Alt-F7 pause, Ctrl-Alt-F8 pause, Ctrl-Alt-F9 pause, Ctrl-Alt-F10 pause. If you cannot reach a GUI screen, repeat using longer pauses. Which, if any, F key(s) result in a GUI screen?
Does anything change if you swap video cables between the two displays?
How exactly did you set up two monitors?
What graphics “chip(s)” are you using, AMD, Intel, NVidia, something else, more than one?
How old is this PC?
Exact Input/Output (using code tags](https://forums.opensuse.org/showthread.php/536143-Using-Code-Tags-Around-Your-Paste) enclosing this information) from inxi -GMxx will help us help you, preferably done from a GUI terminal rather than from a full terminal screen. This output will answer the graphics chip and age questions best. If you are unsure how to get this information from your PC to this forum, try this way:
inxi -GMxx | susepaste
and provide the resulting URL here instead. Do also:
If the susepaste command produces errors, go to http://susepaste.org/ and open the Recent link. Sometimes the error is erroneous. If it still errors, try the same way you did for your image uploads by first redirecting inxi output to a file that you can upload, and upload Xorg.0.log in similar fashion.