How do I prevent players from building in certain areas on an MCGalaxy server? Can I allow my players to claim areas of their own to protect their builds? Also, I tried making Grass a kill block, but it doesn't seem to be working. How do kill blocks work? And is there a resource where I can get the answers to these questions myself?

For changing permission of who can build in a level: /help perbuild
For changing permission of who can build in a specific area of a level: /help zone
(os: /os zones)

Grass won't kill you because you need to pass through it for it to do so. Grass is solid, so you never die from it (unless you noclip).

There is no official documentation for MCGalaxy aside from the README.md on the github page and the /help commands ingame.

1 minute ago, Village_Crafter said:

How do I prevent players from building in certain areas on an MCGalaxy server?

/help zone. More specifically, /zadd <name> <build permission>.

2 minutes ago, Village_Crafter said:

Can I allow my players to claim areas of their own to protect their builds?

You could set the world's permission to the default player rank and allow them to use /zone by using /cmdset zone <rank>, but it can be abused very easily. Would be better if you let players have their own /os realms. You can do that by going into properties/ranks.properties and changing the overseer worlds limit (maybe it's worded differently, idk) to whatever you want. Then, ingame, do /cmdset overseer <rank>. That way, every player can have their own realm which they have full control over.

4 minutes ago, Village_Crafter said:

I tried making Grass a kill block, but it doesn't seem to be working. How do kill blocks work?

I'm pretty sure solid blocks won't work as killer blocks. You'd either have to put nerve_gas above the grass, make the grass have collide 0 (/lb edit 2 collide 0), or enable survival death with falling (not recommended, a bit buggy).

5 minutes ago, Village_Crafter said:

is there a resource where I can get the answers to these questions myself?

Ask around ingame, on the forums or on Discord, use /help, look at past discussions on the forums. For more technical stuff look at the source code if needed.