If you modify the code, you need to explain it in the modified file.
In the extended code (the modified code and the code derived from the source code), it is necessary to include the description of the agreement, trademark, patent statement and so on specified by the original author in the original code.
If the redistributed product contains a notification file, an Apache license is required in the notification file. You can add your own license to the notification, but it cannot be displayed as a change to the Apache license.