New young crimson rosella is a bit confused about life

[zypria]

I apologize in advance if this post is in the wrong place, I need a bit of general advice here. I'm slightly worried.
4 days ago I got a young male crimson rosella. Besides him, I already have a pair of red-rumped parrots. I've previously had couple of budgies.
In short - I don't think I've ever had such a young bird before. I expected him to be scared, wary or aggressive and he's none of that
He just doesn't know what to do
Figured that it's safe to sit at the top of his cage and doesn't dare to explore the vast living area - his own and our apartment. I'm not an expert but he is kind of large and heavy, doesn't fly much. Maybe eats a lot as well. Doesn't get the concept of vegetables, only edible greenery is apple.
On his first day, once out of the cage he latched onto red rumpeds for guidance. Followed them around, called for them, tried to eat with them etc. I would say he was happy and learning what is what. Unfortunately, his foster parents became very mean the next day and had to be separated from this very confused baby. Since then he's been quietly observing but makes no effort to interact with his surroundings or people around him.
I don't think he's scared of anything in particular, he's eating from my hand. I'm just worried that he's not active enough and maybe is overeating. Also he's very quiet. Can I help him somehow or should I just leave him be? We're talking to him but he's ignoring us sometimes. Is this the natural process of adjusting to new environment?
I just want him to be happy, he's one very sweet bird, albeit clumsy

Also how can I teach him to step up? It's not about trust, he's not scared of sticks or fingers, but he doesn't understand that he should step onto it. If I approach from the front he ignores me, the only way is to literally lift his feet from the back, but he steps down right away, very clumsily. He loves millet but won't bother with stepping onto anything in order to reach it so I'm out of ideas

 

[wrench13]

At 4 days, he is still acclimating and becoming attuned to his new home. Let him settle in, observe his actions etc, until you are certain he is done. I'd try to figure out what his favorite treat is ( i use small pieces of pine nut for my 'zon) and then that becomes your training tool. When training, be very observant and reward when there is any progress to the goal. So in step up training, if the bird picks his foot up, that gets the reward, and then you build on that. Rewards have to IMMEDIATE, so he can connect the reward to the action. Have the treat ready. Be very consistent in the way you ask for a given action, so he does not get confused. For step up, i say "Up Up" and put my flatted hand in front of Salty, so 2 triggers, one verbal one hand signal. If there are others in the family that will interact with him, they too should use the same as you. Corellas are very smart parrots. Give him a chance to settle in and I bet he will be like a sponge!

 

[zypria]

At 4 days, he is still acclimating and becoming attuned to his new home. Let him settle in, observe his actions etc, until you are certain he is done. I'd try to figure out what his favorite treat is ( i use small pieces of pine nut for my 'zon) and then that becomes your training tool. When training, be very observant and reward when there is any progress to the goal. So in step up training, if the bird picks his foot up, that gets the reward, and then you build on that. Rewards have to IMMEDIATE, so he can connect the reward to the action. Have the treat ready. Be very consistent in the way you ask for a given action, so he does not get confused. For step up, i say "Up Up" and put my flatted hand in front of Salty, so 2 triggers, one verbal one hand signal. If there are others in the family that will interact with him, they too should use the same as you. Corellas are very smart parrots. Give him a chance to settle in and I bet he will be like a sponge!

Thank you for your reply! (I forgot my contact info oops, would've replied sooner)

I'm proud to say he's doing great actually. After he acclimated to us it took him only one training session to step up. I was surprised at how fast he's picking things up. For now he will only step on my hand if there's food involved, will lightly nibble on fingers if the treat is delayed. Other than that he appreciates the attention in form of talking wih him and lightly petting his chest. But looks rather offended if there's a hand in front of him without a treat, stares at me as if to say "why should my very pretty self come to you?"
He has an interesting personality