Hello, overbrunz. Here are my opinions.
1st - Wich is the most user-friendly distro of linux?
A lot of people will have a lot of opinions. Linux Mint seems to be a hot topic here. It is a fine OS and I have installed it and used it on several machines; but in my experience, it always has bugs that are a pain to get rid of.
As a noob, I would suggest you stay away from the unconventional desktop environments until you get your feet wet. By unconventional, I specifically mean Unity (Ubuntu) and Gnome 3 (Fedora, among others). These are great OSs, but there is quite a bit of a learning curve and I would hate to see you get scared off so soon.
Personally, I would suggest Zorin OS as a beginning Linux distro. The look and feel of the default DE is very close to Windows 7, so most people do not have much of an issue starting up. Once you feel comfortable, you can try out others, like Ubuntu or Fedora, to see if you want to try something new.
2nd - can you gimme some tips on what i should do first in security issues and apps i should use?
As far as security goes, most major distros are very secure out of the box. You might want to disable some ports or add antivirus software or something like that, but, generally, you should be fine with the default security.
As far as the apps go, it all depends on what you use the computer for. Most major distros will come with office software, an internet browser, a music player, disc burner, and other software like games and a calculator. Some, like Linux Mint and Ubuntu come with so much that you will probably not use most of it.
If you are looking for security specific apps, then it depends on the OS you choose and the specific security issue that you are worried about.
the main use i give to my laptop is internet browsing and some ocasional downloads
thnks very much for all the help guys
Give Puppy Linux a try if you do not want to permanently alter you computer. Or, you could try any distro to surf the web and download songs. But, my recommendation is for Zorin OS.
Hope this helps.