I think you need to explain in a lot more detail. We don't know what you mean by "when the system backs-up", we don't know what you mean by "I lose my photos". We also could use the standard set of information as stated for the Adobe community:
Having the "Cloud" does not mean your photos are in the cloud. Are you using the Lightroom app or the Lightroom Classic app? The Lightroom app uploads your photos to a cloud, so they are safely backed up there. Lightroom Classic does not actually import anything into the catalog, it just references them on a hard drive. We need to know a lot more about your workflow to help you.