Gaming + Streaming = network congestion?

So, my problem is relatively simple: When I'm at home gambling and my parents use various streaming services like Netflix at the same time, the network is overloaded and puts a strain on both parties.

I would like to know if there's a possibility to prevent this. Buy second internet connection? Any hardware?

Gamble online? Then the Internet speed of the provider is not sufficient. Order faster line.

If it were that simple. But that is not the case, the line is not bad. Unfortunately, I do not know any more exact technical data. LAN parties have so far always been problem-free and otherwise there are no complaints. Just stop at Netflix and gaming at the same time. Since they have now also Sky, it will not be so for me…