Im op so why do i get this msj? "Failed to give you 1 items,you are not allowed to overwrite items!?

Being OP doesn't bypass the items-Overwrite: false boolean set at the top of your items.yml.
If you wish to overwrite items simply set it to true.

Hopefully that answers your question :)

Thx you that fixxed it,also if you are kind to help me,how can i set up so they cant drop only the compass?when i set up like this
nobody can drop any items,i want this to be just for the compas,not to all the items from the game
Prevent:
Pickups: true
itemMovement: true
Self-Drops: true
Death-Drops: true
Bypass: OP

I sincerely apologize for the late reply, The info you provided are GLOBAL modifiers so they apply to all items.
If you want actions to apply only to specific ItemJoin items you need to add itemflags.

Simply add itemflags: self-drops, death-drops, item-store to your compass item.

See itemflags here; https://github.com/RockinChaos/ItemJoin/wiki/Creating-Items#defining-an-items-itemflags

EDIT: Closing due to inactivity, a new official release of ItemJoin has just been approved.
You can now download it here; https://www.spigotmc.org/resources/itemjoin.12661/download?version=451699