Dissapearing of free space on my HD

[Groover]

Hi all,
Recently I faced a broblem of disappearing free disk space on my hard drive.
I googled this issue, but still I'm not sure what to do. Is that junk files, or maybe too many duplicates... or.. I don't know what else. I would greatly appreciate it if you could suggest any reliable tools to get back that fast dissapearing free space on my disk.

Thank you in advance!!