celkon a67 mobile android-unfortunately android has stopped-showing message

[Android Question]

recently i am using celkon a67 mobile, i don't know why the message is showing always , i am unable use my contacts & all images in my gallery became 0 images- some error symbol is showing on screen when i press messages icon, it'll go & comes again later & when i am trying to use phone message is " unfortunately launcher has stopped " and sometimes "process com.android.com ". please help me to get rid off this inconvenience for ever.

thanks in advance.