when do someone get banned like when do scratch team stop giving them changes

Technically even banned users have chances. Those who are banned for longer than a few days are usually given the option to appeal their ban. This means that they have to write a message to the Scratch Team, explaining that they understand why what they did was wrong, and promising that they won't do it again. If the Scratch Team accepts the appeal, then the user is unbanned.

Sometimes, however, a Scratcher continues to break the rules even after they were unbanned. After 2-3 separate appeals (there is no set number; it depends on many things), the Scratch Team may decide not to entertain any more appeals (since the user clearly isn't changing their behavior), at which point you could say the Scratch Team stopped giving them more chances.