Hi Вербицька М,
Thank you for reaching out. My name is Leo, a user just like you. I'd be happy to help you with your concern.
May I know what device you are using? Different device may have different options to leave a team in Teams. Are you using a browser or the Teams app? To leave, please follow the steps below:
You can leave a team at any time by choosing the team name, and then selecting More options (...) > Leave the team. You'll receive a confirmation message to make sure that you want to leave the team.
Note: You can leave a team on your own, but only an admin can remove you from an org or an org-wide team.
For more detailed steps with corresponding images, you can refer to the link provided below:
https://support.microsoft.com/office/e481005d-3ec6-4694-b300-375472ba4076
I hope I provided a helpful solution regarding the issue! Let me know if you have any further questions.
Best Regards,
Leo