I understood that this is disrespectful to the sukkah or something like that. They talked about it in my synagogue; they said you must not bring pots in, chat idly, etc. I don’t know whether that’s actually Jewish law or maybe some mystical idea (the ushpizin are in the sukkah and you’re talking about soccer?).

There is nothing improper about a person speaking mundane matters in the sukkah. Therefore, someone who wants to talk with his friend face to face or on the phone should preferably do so in the sukkah, just as he would in his home, for whenever he is in the sukkah he fulfills a commandment (Shulchan Arukh 639:1). Likewise, those who want to play chess or Monopoly and the like should preferably play in the sukkah (see Mahari”v 191, Darkhei Moshe 639:1). There are those who are especially meticulous to increase their sitting in the sukkah, and are also meticulous not to engage there in mundane matters (Shelah, Kaf HaChayim 639:5-6, and see Mishnah Berurah 2). Nevertheless, even someone who wants to engage in mundane matters should preferably do so in the sukkah and thereby fulfill a commandment, rather than leave the sukkah in order not to engage there in mundane matters.

A quote from Peninei Halakha on Sukkot

I don’t understand what the problem is with “the ushpizin are in the sukkah and you’re talking about soccer.”

How do you know that King David wasn’t a soccer fan and wouldn’t enjoy joining the conversation?

Soccer was invented in England thousands of years after David.