Hi! Thanks so much for your support.
When you get to the end of a level you need to find the needed item before you leave, usually those items are hidden in that area, I can give you more hints if you want (I don't want to spoil it)... you are doing the right thing! They can be very well hidden, explore very well for hidden paths or access all around the hub, you will find what you need to keep moving forward :-)
If you need more help, please let me know and I can explain how to solve a hub if you feel stuck.
Thanks so much for your support again, I appreciate it very much :-)