I want to start an aio website like it consist of mp3, music videos and 18+ videos which will be easy one click download, do we want to get licence or is it enough if we mention thanks.
If you don't have a license, you can't legally offer the file to download, unless it is shared with one of a select number of free licenses that don't require attribution. A "thanks" is no legal protection against DCMA takedown notices and RIAA or MPAA lawsuits.
So in short: you need licenses.
If it's not your content (especially if it's music videos) and you are letting people download them (worse if you are profiting from it) you will probably get in trouble with those who actually own the content.