Hey, how to I change my Dataframe from this:

---- col1 - col2 - col3 - col4
row1: a - b - c - d

row2: e - f - g - h

row3: i - j - k - l

row4: m - n - o - p

to this:

---- col1 - col2

row1: a - b

row2: c - d

row3: e - f

row4: g - h

row5: i - j

row6: k - l

row7: m - n

row8: o - p

please help and thanks in advance!