How to say, "Could you please move over?" (Cantonese and Mandarin)
There are a lot of ways to ask people to move aside to give room

Mandarin: 

能請你坐開些嗎? (would you please sit aside a little?)

能請你騰一騰空位嗎? (would you please make some room for me?)

Cantonese:

唔該坐過啲 (please site aside a bit)

唔該坐開小小 (please sit aside a little)

In Cantonese, to ask people to move aside, we say 唔該借一借, or 唔該借歪, you can use these phrase in your example too