@hariskar It looks like your root partition ‘/’ has 1.8T or 1800GB of space. The command I would have run is df -h to give you usage. but assuming that debian is less that 50GB you should have plenty of space to capture a modern computer with 50GB of data. Use single disk resizable to use zstd to compress that 50GB of data down even smaller.
What error message are you getting? A screen shot of the error might help set the context of the error.