First of all thank you very much guys for your help. I have had no idea what to buy so your tips were essential! These are all the users that helped me:
erickdiaz84 original_jazzman retardedpanda1 m52nickerson Radox IMojoe134 deadmc26 RubyJunk twizzzdv2 jipster69 MightyAlFred Liam81
Thank you again!
Now to the computer. 1) Price: It is possible that you can buy the same parts for much better price... Well I couldn't. I am Czech and here are just 3 major e-shops, where you can order these parts... the prices are everywhere almost the same. Amazon doesn't exist here and Ebay works just in Germany and that would mean to wait at least 10 days for the shipping + future complications with the warranty.
2) Build: It really was my first time and it also looked like it. I was trying to build it for almost 9 hours. After that I finally managed to install the OS (1:30 AM)... unluckily not even 30 minutes from installing all the needed drivers the PC got infectet with E-shield (Trojan horse) and so I decided to reinstall it, format all the hard drives, because there was no other quicker solution to it... Apropos I have already installed Avast and the only other two programms I downloaded and installed were Mozilla FireFox and KMPlayer - all from official websited... so I still don't know how I could happen, maybe some of the drivers were infected (had to download them from the official MSI page and boot them from a flash drive) It looks like it works properly now. But connecting all the cables and puting all the parts together was a nightmare. It really sucks, when you don't know how much force you can apply to put something together... for instance the CPU into the motherboard or the PSU cabels - not all of them make the "click" sound. However if it will remain at it's current state I find it a very interessting experience.
3) Cable management: I finally understood why almost everybody recommended me to buy a modular PSU. Yes, it was a huge pain to hide all the unused cabels. It doesn't look good anyway, eventhough I was trying pretty hard, but same of the cabels were just too short and I wasn't able to do it other way.
I hope I will find a way to add some photos.