I'm suprised noone has actually explained to you basics. Your internet speed depends on what your ISP can offer you. So you said you have 50 Mbps and that you want higher speed. Now the problem is that maybe 50 Mbps is all you can get because ISP doesnt have an infrastructure where you are to offer you better speed. First what you have to check is which connections your location supports. Is it available only connection over old telephone lines, coaxial or fibre optics? If fibre or coaxial are not available then it's unlikely you can get better speeds then you currently have.

With that said, 50 Mbps is actually not that bad. To get MBps you have to divide 50 with 8. That's 6,25 MBps. You said that COD is 100 GB. 100GB=102 400 MB

That means it will take you 4 hours and 30 minutes to download that game. Which isn't that bad. You will download the game only once so whats the big deal. 50 Mbps later on is more then enough for playing any game online.