Few questions about main mastery changing and armors

[Jakkqlo]

Hello.

I've got some questions about a stat in the armors, for example if a armor has 9.8% mag reiforce it means my magic atk will be increase 9.8% or it means my defense against magic atks will be increase 9.8%?

Ive got a hybrid spear cold, im thinking about changing ice to lightning, reseting my 30 cold lvl and start over with lightning, do you guys think im doing a wisely choice?

Thanks for your attention, and sorry for any bad spelling in english.

[ArJuN]

It means your defense agaisnt magic attacks will be increased by 9.8.
And im not sure about the spear, since im a blade user and dont know much about spear uses =\