I need help in coding my second datapack(I am not at all experienced in coding)

So  I want to code a minecraft datapack and the concept is-
Every player has a timer on his screen. Whenever someone joins, he has 100 hours on his timer.(The timer starts when the player joins the server first time and is always active even when the player is offline)
When the timer hits 0 then the player gets banned of the server
When a player kills someone, he recieves 5 hours 
when a player dies, 5 hours are removed from his timer
A custom item which adds 20 hours on the timer of a player
A custom item which can revive a player who gets banned from the server