1.Where to get / buy a helmet?
2.How do the sword is glowing?
3.I fought on the battlefield (I Level 15) and people from the second killed me easily. I raise each level 5str 1dex 1rec. Why did they kill me easily?
1. A helmet can be acquired from a quest. This will vary depending on your class and faction, so unfortunately I cannot provide you with more information regarding this.
2. The sword is glowing due to it's enchantment level. Above level 5 it starts to glow, with each level above 5 increasing it's glowing and particle effects. Enchantments can be done through the use of Lapisia (Weapon and Power for weapons, and Armour and Defense for armours). Be aware that the Weapon and Defense Lapisia will break your items upon a failed enchantment, but the Power and Defense variations will not. Please view the screenshot provide here for a preview of a sword with an enchantment level of 5: http://i.imgur.com/r9kxt.jpg
3. To stop people from killing you easily, it would be wise to link and enchant your gear. Linking your gear with Lapis will give you more stats, so you could, for example, link a Safe Lapis to increase your REC. Enchantments on your armour will allow you to absorb damage dealt to you by 5 per level. For example, if you have an enchantment level of 3 on your chestpiece, leggings, boots and gloves, you will absorb 60 damage (effectively lowering the opponents damage by 60).
I hope this answered your questions well enough to your liking