Xbox One has Internet problems despite wireless connection what to do?

For a few days I have the problem that I have great problems playing online or not at first play. However, another Xbox One and all phones have a very good internet connection. Does one have an idea why this could be and / or how I can fix the problem again?

So if I can advise you then the following.

Always use a cable!

So you have the best possible connection and are free of interference.

Thanks for your quick response, however, it is not possible for me due to my Zimmerlage a Lasting opportunity to play with cable

What amazes me is that the other Xbox is right next to mine is trouble-free and runs perfectly