What should be better strategy to extract the curves of this photo

edit

How can I extract coutours within this photo?

Running sharpening filters make it worse only

I'm trying to extract counters like this:

cnts = cv2.findContours(gray.copy(), cv2.RETR_EXTERNAL,
                            cv2.CHAIN_APPROX_SIMPLE)

I've done this sharpening:

image = cv2.imread(file)
    height, width, channels = image.shape

    kernel_sharpen_1 = np.array([[-1, -1, -1], [-1, 9, -1], [-1, -1, -1]])
    kernel_sharpen_2 = np.array([[1, 1, 1], [1, -7, 1], [1, 1, 1]])
    kernel_sharpen_3 = np.array([
        [-1, -1, -1, -1, -1],
        [-1, 2, 2, 2, -1],
        [-1, 2, 8, 2, -1],
        [-1, 2, 2, 2, -1],
        [-1, -1, -1, -1, -1]]) / 8.0

    output_1 = cv2.filter2D(image, -1, kernel_sharpen_1)
    output_2 = cv2.filter2D(image, -1, kernel_sharpen_2)
    output_3 = cv2.filter2D(image, -1, kernel_sharpen_3)

    cv2.imshow('Sharpening', output_1)
    cv2.imshow('Excessive Sharpening', output_2)
    cv2.imshow('Edge Enchancement', output_3)

    cv2.waitKey(0)