Windows Update may slow down your internet since it occupies some of the bandwidth. Thanks to Build 16237, now you can limit how much bandwidth Windows could use to update its system.
Follow these steps to limit Windows 10 update bandwidth speed.
1. Go to Start Menu > Settings. Next, select Update & Security.

2. On the Windows Update menu, click Advanced options.

3. Scroll down and find Delivery Optimization.

4. Then, select Advanced options.

5. Finally, adjust the bandwidth percentage as you wish.

Despite all of that, Microsoft may override the setting especially when there’s a very important security update. They want to make sure most their users can get the latest patch.
In addition, disabling Windows 10 background apps could help minimize unexpected bandwidth usage.