[salutsalut]

I have found this

with instance_create(
    x+lengthdir_x(80,image_angle),
    y+lengthdir_y(80,image_angle),obj_bullet)
{
 xspeed=lengthdir_x(10,other.image_angle)
 yspeed=lengthdir_y(10,other.image_angle)
}

or this one

with instance_create(
    x+lengthdir_x(80,image_angle),
    y+lengthdir_y(80,image_angle),obj_bullet)
{
 xspeed=cos(other.image_angle*pi/180)*10     //convert degrees to radians when using these
 yspeed=-sin(degtorad(other.image_angle))*10 //i think the y component needs to be flipped
}

but I can't match it with your code.