To solve Brawl Stars connection problems, there is little you can do if the issue is external. If the game servers are experiencing abnormal behavior, then it is up to Supercell fix it, and not you.
Now, let's assume you are playing in your living room and the router is in another room. Depending on the distance, this should not be a problem, but there are occasions when the sign of a lost connection may appear, which could have catastrophic consequences for your game. There are two methods to solve this problem: playing on a computer with a wired connection and an Android emulator or moving closer to the router for a better WiFi signal.
Keep in mind that, lately, Supercell games are plagued by connectivity interference: when you start playing a game, the wireless signal your device receives drops dramatically if you are not near the router. This way, the servers cannot connect you, making you automatically disappear from the game.
And it is not just a matter of a few users, as it is something that has been going on for quite a time. Supercell has long been asked, almost implored, to solve this problem, but for now, it persists. We hope it will be solved soon.