Hi there and
to the forums!
You've come to the best possible place to learn about the best practices for keeping budgies!
Your little boy is probably very scared right now. As mentioned, it's important not to try and touch or tame him in the first few weeks you have him. Runny/green droppings are normal when you first bring a new bird home as they are a sign of stress. As he settled in, his droppings would have returned to normal.
You've been given great advice to help him feel at home!
Please let us know how he's settling in!
Be sure also to read through the links provided above by FaeryBee. You'll find all you need to know about budgies within! If you have any questions after reading though everything, be sure to ask as we'd love to help!
We hope to see you around the forums!