Thank you for your question and reaching out. I can understand you are having query\issues related to Two internet lines.
You need to place Firewall or Router so that You can divert or filter traffic based on some rules
Or if both lines are connected directly to your Windows Computer
open the Network and Sharing Center -> click on Change adapter settings in the left pane. you should see a list of network adapters. Press the Alt button (if the menu bar is not already visible) and click on the Advanced menu, and then choose Advanced settings -> A new control panel will pop up, and you should see it open to the Adapters and Bindings tab. In the top list should be a list of your network adapters, with an up and down arrow button to the right.
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