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We've created an article to guide you on how to improve your WiFi connection at home. Refer to this link.
The 2.4GHz has a wider range, but is prone to signal interference. While the 5GHz has a shorter range, but has less signal interference which may provide you a better speed and stable connection.
In order to boost your WiFi connection, you need to get an extender or a mesh network to cover the whole house.