I bought a Mac PC for managing my Apple devices more easierly. I bought a Mac PC for managing my Apple devices more easily.

It is themy first time in the Mac environment, so I am not familiar not only to useusing a Mac, so not only am I unfamiliar with using a mouse device, but also with how to copy files, to manage them, and so on. It is my first time using a Mac, so not only am I unfamiliar with using a mouse, but also with how to copy files, manage them, and so on.

It sfeemls like that I just arrived in a new country. It feels like I just arrived in a new country.

I think "feels" works better than "seems" here. You could also say "It's like I just arrived in a new country."

My old experiences are not suitable fordon't apply to this new environment. My old experiences don't apply to this new environment.

But this PC reduces my stresses about using my Apple-made devices. But this PC reduces my stress about using my Apple-made devices.

I would probably write this as "But this PC makes using my Apple-made devices (easier/more convenient/less stressful)."

It is more easyeasier to copy musics into my iPhone, and it is convenient to manage files from my iPad. It is easier to copy music into my iPhone, and it is convenient to manage files from my iPad.

It's always just "music" whether you're referring to one song/style or many.

I think, using this PC will makbe many interesting experiences for me. I think using this PC will be an interesting experience for me.