I installed GPG4USB onto my usb stick.
Works in windows.
But tails doesnt recognize the start linux launch button and asks to open it with another programm....
How to make it work ? Do I have to select a specific programm in Tails to run it through it ?
Thx
(Tried to create a persistent volume in tails on usb but
it lacks uefi support so I cant do it with my 3.0 Usb slots.)

I fear GPG4USB won't work inside Tails.
You should instead use GnuPGP, the free software implementation of OpenPGP that is included in Tails.
You can also read the documentation pages related to its usage: