Hi Shapulia, welcome to CDFreaks!
DVD recorders are not meant for copying DVDs, although some of them will copy DVDs that are not copy-protected. Even for DVDs that are not copy-protected, copying will be much slower than when doing it on a computer.
Your Sony RDR-HX780 will not copy CDs at all and it will not copy any DVDs that are copy-protected.
If you want to copy DVDs you should use a computer with a DVD burner instead.
A HDD/DVD recorder’s main purpose is to record TV broadcasts and watch them later and also play DVDs, usually with added features such as playing Audio CDs, MP3 files, JPEG files etc.