If you find issues with embedding a gif (i.e. sizing issues, it redirects incorrect, etc.), then you would want to reach out to a Shopify Expert or create a new thread here on the Community Forums to seek further assistance. Shopify is unable to provide troubleshooting support on third-party coding; however, creating a new thread will increase your chances of this issue being seen by someone in our Community that may be able to assist you.
I was desperately searching for the solution. I found this video on Youtube. This guy explains it very well! Thanks to him I am finally capable of adding GIFs, if the GIF is too big on mobile devices go for ´´Small´´ and not regular link. The link still has to ends with .gif
Hopefully it is going to help you all :-)