so far i got a working following companion that i can equip with openTeammateContainer 1

but now i'm trying to figure out how to make him use his inventory so he runs out of ammo , weapons and armour will break

is this possable to do in GECK ?
or will i need to use fose

the armor breakage - - - I suggest forgetting about it. It simply doesn't wear out when followers wear it and it seems to be to be an .exe thing. You don't want to even script that IMO, I have not bothered for Phalanx because of what a pain it would be.

The weapon WEAR, forget about it - they actually have an .exe based auto repair effect that kicks in now and then. I couldn't tell you if the effect is intentional on the part of the developers, but it is positively there. Equipped weapons can take DAMAGE (like if someone shoots a missile at your follower), but it's not the same thing.

Using ammo. In your followers base definition in the GECK, DO NOT put ammo or weapons in there, except for one weak melee no-drop weapon like a Charon's Combat Knife, specifically. They have to be defined without ranged weapons and ammo to work semi-normally. Then, when you pass the follower regular weapons and ammo in-game, it'll be used somewhat normally.

There is also a flag on the weapon data page that, if ticked, will allow "NPCs use Ammo". But this requires making a customized gun for them to use.

Yeah, but it's not necessary if he's looking to pass the follower a weapon and ammo for it and have it work as expected. PlayerTeammates will always use ammo for "playable" type weapons that they have. This may be new for Fallout 3 as opposed with Oblivion, I may have read that somewhere.