If you provided your email address when registering, you can reset your password yourself. To do this, go to the login page of your school and click on "Forgot your password?".
You will then be asked for the e-mail address you have saved. As soon as you have entered and confirmed this, you will receive a link to this e-mail address with which you can reset your password.
If you do not receive an e-mail, it could be that you have saved a different e-mail address in Sdui. Try again with a different email address.
Alternatively, it could be that a typo has crept in during registration. In this case click on "No e-mail address given?" and follow the instructions.
After resetting the password, you will remain logged in on your end devices. In the article "How can I log out of all devices?" you will find the instructions for logging out.