Hello i got a question!
If i buy a helmet whic has a normal resist
an armor for fire and ice resist
and a shield for shawdow resist(radnom items) i always get these resists or i need to use my shield to get them?
Armors and elementals

There's not such thing as Normal Resistance or Shadow Resistance. You're completely confusing Damage with Statuses and Defence with Resistance.
Defence protect knight form damage. There are only four types of damage: normal, piercing, elemental and shadow.
Resistance protect knight from statuses like stun, fire, poison, curse, freeze, shock and sleep.
Statuses are special negative conditions, like slowing down, inability to heal, lowering damage output and so on.
There's no such thing as fire damage or ice damage.
Statuses and Damage are not related in any way, for example there are attacks that deal Shadow Damage and cause Shock or attacks that deal Piercing damage and cause Fire and so on.
Shield does not provide any Defence or Resistance to the knight.
Shield, if activated, just takes damage instead of knight. Shield's stats indicate how many damage it will absorb until it breaks. For example shield with Shadow Defence is able to absorb more Shadow damage then Shield with Elemental Defence.
Shield with Status Resistance will absorb more damage from a monster that cause given status. For example Shield with Shadow defence and Freeze resistance will absorb more damage from a Frozen Shambler (type of zombies), then Shield with the same Shadow defence, but without Freeze resistance.
Aha now it's more understandable thank you guys you helped me a lot!
This might help you understand damage/ defense in Spiral Knights:
http://wiki.spiralknights.com/Damage
Here's a page with a list of all armors (which most of the time has a helmet with equal defenses)
http://wiki.spiralknights.com/Armor
Shields work a little differently; it is like a separate... thing. It has its own health and defenses, and only when it breaks, will you start taking damage (which is when your armor takes effect).