Creating derivative work based on a project under apache license - Dealing with original notices in source codes

There is a library licensed under Apache License 2.0 that I extended its functionality in multiple new Classes. Also some of the original Classes of the project had to be modified in which some of them slightly changed but some modified a lot. Multiple new methods was added and some older methods changed and some moved and etc. Now I think the library is more useful than before.

I know in Apache License one can create a Derivate work from an original source or object.

Subject to the part 4 of the license (4. Redistribution), I created prominent notices in modified files that I modified or added these parts.

Also I'm going to bring the original Notice files and also any materials are needed to show my respect and thanks to the original work.

Now my problem is in the modified files. Above each file, there is a notice like this in the form of comments:

Licensed to the SOME_NAME under one
or more contributor license agreements.  See the NOTICE file
distributed with this work for additional information
regarding copyright ownership.  The SOME_NAME licenses this file
to you under the Apache License, Version 2.0 ...

I don't know how to deal with those notices. For example in the case of notice files, I can put

Copyright [yyyy] My Identity

in the original Notice.

But in the source files, should I keep that notices about

Licensed to the SOME_NAME

above the modified source codes even though I've modified them?

Also I don't know its worth mentioning or not that I'm going to keep the license to be as Apache in my work.

Thank you for your interest in subject and helping me.