I keep getting errors please help this script is to make gui appear if trigger is on

 var Itemname = "Oak log";
 var Itemdiscription = "some something to keep chills away";
 var Itemworth = "worth-100gp";
 var ItemBox = 1;
 var ItemBoxWidth = 300;
 var ItemBoxHeight = 235;
 var ItemBoxsize = 100;
 var ItemBoxsize1 = 100;
 var Buttonwidth = 200;
 var Buttonheight = 235;
 var Buttonsize = 80;
 var Buttonsize1 = 25;
 var Text1 = "Description";
 var Buttonwidthx = 200;
 var Buttonheightx = 260;
 var Buttonsizex = 80;
 var Buttonsize1x = 25;
 var Text2 = "Drop";
 var details : boolean = false;
 
 function start(){
     function OnTriggerEnter(other : Collider){
         if(other.tag == "Player"){
         details = true;
         }
     }
 
     function OnTriggerExit(other: Collider){
         if(other.tag == "Player"){
             details = false;
         }
     }
         if ( = true){
         function update
     }
 }
 
 function update(){
         function OnGUI(){
         GUI.Box(Rect(ItemBoxWidth, ItemBoxHeight, ItemBoxsize, ItemBoxsize1), Itemname);
         GUI.Label (Rect (300, 24, 100, 100), Itemdiscription);
         GUI.Label (Rect (75, 130, 100, 100), Itemworth);
         //text color
         GUI.color = Color.white;
         if (GUI.Button(Rect(Buttonwidth,Buttonheight,Buttonsize,Buttonsize1), Text1));
         //Button
         if (GUI.Button(Rect(Buttonwidthx,Buttonheightx,Buttonsizex,Buttonsize1x), Text2));
     }
 }