Photo App for Galaxy S7

I'm looking for an App which I can use on a Galaxy S7 as I need to resize an image.

I can crop the image but I can't reduce the size of it.

I'm abroad at the moment and it's very difficult to post large images to FB from my mobile.

I have Lightroom on my S7 but can't see how to resize image.

No problems posting on laptop as I have Photoshop CC on there.

Camera app