What build (n00b)

first shoudl i go mes/ele or mes/nec (or something eles if you want to thro it out there) and then what build should i go

Secondly i keep hearing about this interupt/shutdown build and what is that exactly and should i use it and does it require pure mesmer?

Firstly, read up on things. There are plenty of ideas around here.
We can't make that decision for you.

If you ahve this much trouble, maybe you should play a more straightfoward class ^_^ Mesmers require a bit of creativeness at earlier parts in the game >_>

well what is a slowdown/interupt build i mean is it pve or pvp"?

I started out as a Me/Ele and eventually went to using all mesmer skills because as I became more experienced with using them, I realized just how important/useful they are. Later in the game (Droknars and on) an Interrupt/Shutdown Mesmer makes the game much easier. Shutdown has to deal with taking energy away from your foe so they can no longer cast and Interrupt has to deal with stopping them from completing a cast.

Once again, if you read up on these builds, you'll know what they are. I'd recommend playing the game with another class first. Honestly. Once you play through, you'll know what the enemies in all the areas are like and you can build around that. Mesmers are the designed to shut things down and use punishing spells, but if you don't know which to use then you're screwed ^_~

I suggest an Elementalist/Mesmer. That way, at least you can use the Mesmer interrupts if you choose (since they're 0.25 seconds to cast, you won't miss Fast Casting that much).