[Xrystal]

This is the new go to place for API help for WoW
https://wow.gamepedia.com/World_of_Warcraft_API

I would suggest looking at some small recent addons to see how things are coded now to give you a start and then slowly relearn some of the addon stuff thats still hidden somewhere in your programming memory

What I find useful is to create a template addon so to speak that has the pure basics and then build any specifics into it for any addon I want to write.

For example:
This is a simple addon template that nearly all of my addons have used as their starting point. Feel free to utilise yourself if you want.

Good Luck

--[[ Localise the Addon Wide Data Table ]]--
local addonName, addonData = ...
 
--[[ Localise any Addon Wide Sub Tables that are frequently accessed ]]--
local Translate = addonData.Translate
 
--[[ Addon Specific Functionality ]]--
...
 
 
--[[ Monitor registered events ]]--
local function EventWatcher(self,event,...)
    -- Store the arguments into an array to access when needed
    local args = { ... }
 
    if event == "PLAYER_ENTERING_WORLD" then
       -- Deal with player entering world
   elseif event == "ADDON_LOADED" then
      -- Deal with any addons being loaded that you want to watch for ( args[1] is addon being loaded )
    end
 
end
 
local f = CreateFrame("Frame")
f:RegisterEvent("ADDON_LOADED")
f:RegisterEvent("PLAYER_ENTERING_WORLD")
f:SetScript("OnEvent", EventWatcher)