Windows Form Application - Transparent PictureBox Image overwrites Form Transparency

Question

So I set the background of my form transparent by:

this.BackColor = Color.Red;
this.TransparencyKey = Color.Red;

Which works fine, but when I now want to display a semitransparent image with a textbox on top of that, the transparent background of my form becomes red where I draw the transparent image.

Any ideas on how I can stop that from happening ?

Cheers!