Ubuntu 18.04 only showing one screen resolution option

My settings only show one screen resolution in Ubuntu 18.04 :

xrandr -q gives one resolution, as you can see. For my second screen, many resolutions are available.

$ xrandr -q
Screen 0: minimum 8 x 8, current 3840 x 1080, maximum 32767 x 32767
DVI-D-0 disconnected (normal left inverted right x axis y axis)
HDMI-0 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 598mm x 336mm
   1920x1080     60.00*+  59.94    50.00    60.05    60.00    50.04  
   1680x1050     59.95  
   1600x1200     60.00  
   1440x900      59.89  
   1280x1024     75.02    60.02  
   1280x960      60.00  
   1280x720      60.00    59.94    50.00  
   1152x864      75.00  
   1024x768      75.03    70.07    60.00  
   800x600       75.00    72.19    60.32    56.25  
   720x576       50.00  
   720x480       59.94  
   640x480       75.00    72.81    59.94    59.93  
DP-0 disconnected (normal left inverted right x axis y axis)
DP-1 disconnected (normal left inverted right x axis y axis)
eDP-1-1 connected 1920x1080+1920+0 (normal left inverted right x axis y axis) 293mm x 162mm
   1920x1080     60.03*+  48.03  
DP-1-1 disconnected (normal left inverted right x axis y axis)
DP-1-2 disconnected (normal left inverted right x axis y axis)

I tried the answer from this response but what I got is:

PRIME Displays cannot be controlled by nvidia-settings and must be configured by an external RandR capable tool.

That means I cannot control the displays thanks to nvidia settings. So I believe I have to use a RandR capable tool but I have no idea how. Must of all, I had no idea it'd be so difficult to change my screen resolution. How should I do it?

EDIT thanks to comments: my laptop is a Dell XPS 7390.