@Mora_rus yes I did my best with the math part of the lua, but that's still not correct, so like in the video grenades can go out of a portal and get in the same portal with a specific throw distance & angle - also for the same reason sometimes even if you throw your grenade correclty it doesn't work.
I'll maybe comment and clean my code, since many showed interrest on it
thanks everyone
@ Pagyra: if the portal were on walls it would makes sense to come out grenades in the opposite dirrection (like in portal the game). but on the ground it's more like start trek warmhole - same sens - same dirrection - same strength
@ VADemon: thanks for your offer! ok let's improve this script