I don't think Google translate translated your original comment very well, but seeing how you replied in English up here I'll reply in English. The copyright system isn't always easy to understand. It's easy to understand that you cannot use music from other people, but sometimes you can get into trouble for even using pictures, and there these people called "trolls" who will register your content, and then claim your videos. Scammers have been trying to hijack people's channels for years and people are getting smarter, so these "trolls" will go to extreme measures to "troll" you legally which can be very troubling. VidSummit there was a session about the importance of registering and copyrighting your own intellectual properties. I believe Disney has lost of it's rights in other countries, and because of that, legally people make counterfeit of their products and videos which legally they can't stop. I think it registering their name in other countries.
Jon Prosser recently had someone register one of his photos on a website, and then had his account taken down for copyright. It's a very nasty move when someone tries to claim your properties, and then use it against you. This is why you have to register your name on all social media before people try to steal your name as well.
Legalities are challenging. It's easy to say "don't use copyrighted music" but sometimes it gets a lot greyer than that. Technically you can't do cover music without permission. Technically you can't play video games on YouTube without the developers permission, and sometimes there's unspoken agreements between original creators and YouTubers, and occasionally you'll have one person who uses that unspoken agreement against creators because they know not everyone understands how copyright works, and they use that lack of knowledge to exploit creators.
This is why it's important to study law when you can, to know what you can, and cannot do to protect yourself.
Ideally you should have a lawyer, but not everyone can afford to have a lawyer, which is why it's best to learn what you can, to try and keep yourself ahead of the crowd.
