"Hoeveel keer per dag kijk je in de spiegel?"

No, there's a difference between looking at the mirror ("naar de spiegel kijken") and looking in it ("in de spiegel kijken"). With the first one, you look at the object itself (the mirror). The second one, you look at the reflection.

It's "-sp" like in "sport"

It's not incorrect, but it does put emphasis on the -you- part.