How can I "allocate" internet bandwidth to a specific app or device

So, I need to download a huge sized game (GTA 5). Its size is about 70 GB, but as my internet connection is not stable (sometimes fast, sometimes slow) and sometimes is very low, I need a way to "allocate" like 0.5 MB/s (not 0.5 Mbits/s but the effective download speed) to my main computer to me be able to search and use the internet, and the rest go to the other computer, to the download.

Is that possible? if yes how can I do it?

Edit

I will be more specific:

So, right now my download speed is 1.2MB/s, so I want 0.5MB/s go to my Main Computer and 0.7MB/s go to the other computer that is downloading the 70GB game.

Other Example:
If I had 3MB/S download speed, 2.5 would be to the download and the 0.5 to my main computer...

But if my download speed was like 350KB/s all bandwidth would go to my main computer...

Edit

My router does not support QoS and I guess i can't install dd-wrt or openwrt, because the router is from the ISP and it receives the internet via 4G/3G

My router: Huawei B593s-22

1 Answer

For Windows, you could install NetBalancer.

You can set max bandwidth and process priorities, as well as custom rules. It may not give you exactly the flexibility you require. but you can use it to work smoothly. The page I linked to also has a video describing usage.

You could also consider NetLimiter.