Need help with custom script (extra resources)

[Herod]

I really has problem with custom script codes how can I memorize them?
An upgrade requires "Mercury" but is not working.... whats is going wrong with this trigger

• Tech
  • Events
    • Unit - A unit owned by Player 1 (Red) Begins an upgrade
  • Conditions
    • (Researched tech-type) Equal to Blacksmith Upgrade
  • Actions
    • If (All Conditions are True) then do (Then Actions) else do (Else Actions)
      • If - Conditions
        • CountMercury Greater than or equal to 1
      • Then - Actions
        • Set VariableSet CountMercury = (CountMercury - 1)
        • Multiboard - Set the text for (Last created multiboard) item in column 2, row 1 to (String(CountMercury))
        • Set VariableSet Footman_train = True
      • Else - Actions
        • Custom script: call IssueImmediateOrderById(GetTriggerUnit(), 851976)
        • Game - Display to Player Group - Player 1 (Red) the text: |cffff0000Not enoug...

and the trigger to return the mercury if the tech is canceled

• Cancel elven destroyer Copy Copy
  • Events
    • Unit - A unit owned by Player 1 (Red) Cancels an upgrade
  • Conditions
    • (Researched tech-type) Equal to Blacksmith Upgrade
    • Footman_train Equal to True
  • Actions
    • Set VariableSet CountMercury = (CountMercury + 1)
    • Multiboard - Set the text for (Last created multiboard) item in column 2, row 1 to (String(CountMercury))

 

[Cheshire]

custom script codes how can I memorize them?

read this every day 100 times, after your daily 100 pushups, sit ups, squats and 10k run:

1.31 Documentation

Blz native Documentation (new natives and more) 1) General: 8 1.1 Lua inside GUI 8 1.2 Backstory LUA and JASS (1.31 PTR), by 0xeb (Blizzard Developer) 9 1.3 UI FRAMES (For Frame Natives): 10 1.4 (Possibly Incomplete) list of ingame frame names (not counting children): 12 1.5 List of in-game fram...

docs.google.com

 

[Herod]

I didnt find helpme plz one script that cancel the upgrade

 

[Cheshire]

I think this is what you want:

native BlzDecPlayerTechResearched takes player whichPlayer, integer techid, integer levels returns nothing​

Explanation:
Decreases (reduces) a specific player’s specific upgrade by a specific amount of levels.

Even though this native takes an integer and integers can be both negatives and positive numbers, in this specific case this native does not allow for an increment by setting the integer to negative.