Gallery Grid, Hover Color & URL Clickable (SS 7.1)

Hi guys,  I’m completely new to any sort of web design & graphic layout, I m doing ok but I will have quite a few questions - but I’ll start with this one,  in my gallery grid I quite simply want to make a hover colour effect with opacity adjustment & the click through URL needs to work, I’m currently still working in trial mode so I’m not sure I can site share, or can I ? 

I've managed to create the hover effect a few times from CSS I found online, but every time the URL stops working 

Any help would be much appreciated, 

Thanks 🙂

You can use this code.