Suppose your data are in column A, then in the adjacent cell, write this formula:

=LEFT(A2,FIND("-",A2)-2)

Check the screenshot below:

Your formula nearly does it, with just this one change:

=IFERROR(RIGHT(C1,LEN(C1)-FIND(":",C1)), C1) 
                                          ^----- replaced "" with C1 

This formula gives the results:

john
mike
edmund
hello
edmund

Hello,

If ALL your original data values end with a space and a dot and start with "Company: " as in

Company: some data .

Then you can use

=MID(A1,10,LEN(A1)-11)

If it's always just a single hyphen that is hanging out at the end OR the beginning of the word then you could do this with some if() functionality:

=IF(LEFT(A1, 1) = "-", RIGHT(A1, LEN(A1)-1), IF(RIGHT(A1, 1)="-", LEFT(A1, LEN(A1)-1)))

If there is going to by multiple hyphens that need to be removed, I think your best bet is with a UDF:

Function TrimCharacter(inString As String, trimChar As String) As String
    For Each word In Split(inString, trimChar)
        If Len(word) > 0 Then TrimCharacter = TrimCharacter & IIf(TrimCharacter = "", word, trimChar & word)
    Next word
End Function

Just plop that into a new module in VBE, save your workbook, then you can use it in a cell formula like:

=TrimCharacter(A1, "-")

And it will trim all hyphens from the beginning and ending of the word.