If I'm understanding the problem and it's actually called 'bng files' then you need to escape it (bng\ files) or quote it ("bng files") or tab complete it (bng<tab>). And, like qwijibow said, if it's in the root directory, '/bng files' would work but, since it probably isn't, it needs to be the full path (/foo/bar/bng files) or a relative one - plain 'bng files' if its in your current, '../bng files' if it's across, etc. Because of the space, 'cd bng files' means 'change to the directory called bng' - the shell just ignores what it sees as an extra argument to the cd builtin that would mean 'change to the directory called files'.
You say it says 'no directory found' though, and it shouldn't, so maybe I'm misunderstanding. It should have said 'bash: cd: bng: No such file or directory' which tells you exactly what the problem is.