Can't go to head voice

Hi I'm new here and I 14 years old and my voice change 

so when I try to go to the head voice

he goes really high and then

I can't talk

what can I do to fix it?

 how do I get to sing with a head voice for a long time?

and when I was young I go to a high voice easily

there is a technic to get this voice back?

also, I'm stuck in the 4 videos in the:

how to sing like a pop star course cause I can't go to that levels of the voice 

how can I go to these levels?

Hi, Ori! I recommend you start with my beginner course. You'll learn about your voice and get a good foundation in vocal technique! 

For accessing your head voice, sing lightly and quietly; we use an "owl hoot" sound in the beginner course. Over time, it'll become easier to access and sustain!