Hello Ekaterina,
I have checked this from my end. If you set SP Page Builder > Permissions for each group to Delete > Denied, no one will be able to delete pages created by others, except for the root administrator.
However, there is currently no option to allow same user group users or users to delete only the pages they have created. As you may know, this Access Control List (ACL) functionality is managed by Joomla, and it is not something we can control from our end.
Let me know if you have any further questions.
Best regards,