I’m running out of ideas and need help. 
Last week, we hired an engineer to rearrange our internet cables at home. But these past few days, I keep experiencing lag while playing games and even slow video buffering. The engineer assured us that it was a gigabit network and everything seemed fine during installation. Could it be that I got scammed? 
Make sure your network equipment matches your broadband speed. If your router or modem doesn’t support gigabit broadband speeds, you won’t be able to get the maximum speed even if you upgrade your broadband speed.
Before jumping to conclusions that you may have been scammed, there are a few troubleshooting steps you can try to pinpoint the issue:
Check your internet speed: Perform a speed test using a reliable website or app to see if you’re getting the expected speed. Compare it with your internet plan’s advertised speed.
Test different devices: Check if the lag occurs on all devices or only on a specific one. If it’s only one device, its settings or hardware could be an issue.
Restart your router: A simple restart can sometimes fix temporary network issues. Try turning off your router, waiting for a few minutes, and then turning it on again.
Reduce network congestion: If there are multiple devices connected to your network, try disconnecting some and see if the lag improves. Also, ensure that no one else on your network is engaged in bandwidth-intensive activities like downloading large files or streaming 4K videos.
If none of these steps resolve the issue, contacting the engineer who installed the cables might be worth contacting to explain your continued difficulties.