Beginner alert! Please critique

So I've been a dressage girl my whole life and I've never had a single jumping lesson.
I've jumped over little stuff in the arena and popped over logs on the trail but I've never really learned the stuff I should. So I decided it was way past time and I've started taking lessons at a hunter/jumper barn. I plan to teach my horse to jump once she's broke so I figured I had better have a head start. Lol
Here's pics form my first lesson:
I need some serious help on my release; I try to give him his head but I feel like everytime I do he runs off with me after the jump. I also am a chicken appearantly (the arms)

Lovely horse! I don't ride english, but you definitely need to
Work on your posture in the saddle and remember to relax! :P

You look Great!

Relax? What's that? Lol
What do I need to fix with my posture?

Lol, alot of people need to relax when riding, I even have to remind
Myself sometimes!

When I said "your posture," I seen in the first pic when riding
Around the ring you seem to be leaning forward a bit, I would
Straighten up a bit (unless you were about to jump, I don't know).
I think in english riding posture is a BIG DEAL, but like I said
I ride western, but I was giving my honest opinion and help. :P

Do you own that beautiful horse you are riding?

No I wish, his name is Sebastian, he's a lesson horse and an absolute sweetheart. I think he's a thoroughbred; it's quite a change to go from him to my tiny 14.2 Arab. :)

I don't know why I'm leaning forward lol. I'll have to work on that. I kind of had this image in my mind that that's what hunter/jumper riders do.... I always sit up straight in my dressage saddle though.

Thank you!

Your Welcome! Wow, how tall is Sebastian exactly? :)

From what I can tell...
Your release needs work, but for only your first jumping lesson you're doing very good. :)

What exactly should I be doing? Do I need to put my hands up farther on his neck?

I don't know... he's big though. Maybe 16.2 or 3? I forget how tall he is when I get off, and I'm like, where's the ground?

Hmm
Well from what I see in the pics
Instead of giving him tons of rein
Keep contact with his month, and rest your hands on his crest.
This can help with your balance too if you need something to hold on to
When he takes a big leap :)
And i'm sure if you look up show jumping on google images you'll see riders doing it
If I didn't explain it well enough

...i just took another look at your photos
And on the last two you're doing it very well :)