In addition to the above, if you are still having trouble, please tell us the size of your monitor in pixels (width and height) and not in inches. Please tell us the size of your original photos straight out of the camera (in pixels, width and height) and not in megabytes.
Please post your System Information as Lightroom Classic (LrC) reports it. In LrC click on Help, then System Info, then Copy. Paste that information into a reply. Please present all information from first line down to and including Plug-in Info. Info after Plug-in info can be cut as that is just so much dead space to us non-Techs.