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Testimonial Block

I am working on testimonial blocks for my site, and wondering if any one could help me figure out the following: Please see the image below for reference. I’d like the black area to be transparent and the white area to be opaque, and for the hight of the block to be responsive with out changing the line weight of the border shape, or the quotations. Please help, thanks!

Here is my site Read-Only: LINK
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