It sounds as though you may have inadvertently opened an older catalog.
Try File > Open Recent... And see if your up to date catalog with all your work is listed there.
Thanks Mike, but it didn't work, had only one version and the old one :-(, but thank you for taking the time to answer!!
How is it possible that my PC did some updates and now I've lost all my work I did in LR?
Did you move any files using Windows Explorer? Are you using an external hard drive? What exactly do you mean by "lost all my work?"
As well last time I had a problem, I tried to import my copy and it deleted all my content in LR.
When you import pictures into LR the files are not copied or moved. LR merely puts the filename and it's physical drive location into the LR catalog database file. That is all. If you move these picture files or folders from outside LR using Windows Explorer an '!' symbol will appear on the thumbnail and filmstrip. If you reimport those "missing" image files all of your edits will be lost. Is this what happened?
Please use your operating system's search feature to find all files on all hard disks that have a name that ends with .LRCAT
Double-click on each one found until you find the catalog with your photos.
Or you can restore your catalog from your catalog backups. You do have backups, don't you?