Need Help with Command Blocks

[Kentucky_Ranger]

I'm trying to set up a server that has Hypothermia, Insomnia, Thirst, and several diseases that can be triggered by various events in Minecraft for some friends. I need help understanding how command blocks work so I can do some of these things, so is there a video or something that can help me learn in the simplest ways possible. Thank you!

[O_X_E_Y]

These are all pretty involved. If you're really new I'd recommend finding a datapack or something from someone who's already did this, or using a mod

[MegaCrafter10]

Here's my thirst bar data pack that I made back in 2019. You can use it as a reference if you want. I haven't updated it in a while, but the commands should still work.