How to place controls on a form?

Question

Design

I'm trying to make an account connection form in a messenger application.

The user is expected to:

• fill in the login, password, server fields
  
• press the connect button.
  

Also, the user can:

• want to leave this form, without connecting
  
• configure additional connection parameters (for example, port, encoding, etc.).
  

You also need to display the connection result to the user:

• display errors during the connection process, if any
  
• display warnings if some fields are filled incorrectly.
  

Actually, the question itself: what are the considerations, how to do it all?
For example, is it better to add a "cancel" button or a "close" cross button?
Or maybe the "Back" arrow at the top left?
Any, even the most extraordinary options and suggestions are welcome. Thank you!