Stalker NPC why is Skill() script command not working for me

[Atomik 1]

Hey guys ,
 

So i was going through this script , i dont know who it was made by but as i'm trying to learn how to script i read whole script and try to understand how it works 
so i had a little doubt here please help me if u can. 

Here's the Script: https://pastebin.com/myhNdrkj

So as this script pretty much gives u a skill and then stores the skill it gave u in "StalkerSkill"
and everytime u login it checks for StalkerSkill and gives u the skill back . so it isnt lost .

But problem is when u speak to the NPC in order to get a new it only checks for the skill that you obtained from NPC.
So if u have a skill that You got from the NPC it will remove that skill and assign u new one .

But what about the skill that a stalker copied from other player . When m doing that its stacking up 2 skills .

Is there a way to fix it , and if yes how ? 
Please Help me out with this one Guys <3
 

Edited February 17, 2018 by Atomik