merge to values in one cell

M.Yasir Fakhr 

One more

=IF(ROW()=1,B$2&B$3,
    IF(INDEX(C:C,ROW()-1)=INDEX(B:B,ROW()-1)&INDEX(B:B,ROW()),
        "",
        INDEX(B:B,ROW())&INDEX(B:B,ROW()+1)
    )
)

HI M.Yasir Fakhr 

Here is another alternative, using OFFSET()

=IF(ISEVEN(ROW()),CONCAT(A2,OFFSET(A2,1,0)),"")

You have now several options

Let us know what works best for you

David 

M.Yasir Fakhr 

As an alternative, you may use Ampersand (&), like this in B2: 

=IF(ISEVEN(ROW()),

A2&A3,

"")

Hi M.Yasir Fakhr 

You can use Concatenate() to merge values.

=CONCATENATE(A3,A4)

Excel file is also attached for reference.

Tauqeer Ahmed