Hi Hananke,
You can always do an "up do" when you are curly.
That way your bottom half that is straight would be up and not noticeable.
Just make sure you take it down in the evening so your hair can breathe.
I have an up do shot in my picture link.

And as everyone knows...
I love Joiwhip mousse.
I also like Devacurl no poo and condition one. My hair has been growing like crazy since I switched to these products a few months ago.
Good Luck!