Unacceptable Offer from Gulf Insurance for My Lenovo Tablet Repair

A year ago, I bought a Lenovo tablet from Teknosa and insured it with Gulf Insurance. Recently, the front windshield broke, so we sent it to Gulf Insurance to be fixed. But they told me that the tablet couldn't be fixed and instead gave me a gift certificate worth only a third of what the tablet was worth. I don't understand how a small crack in the glass can ruin the entire tablet. Also, I bought the tablet and insurance separately, so how can Gulf Insurance take away my tablet? They have made mistakes like this before, and I won't let this go. I'm ready to go to court until I'm paid fairly.