Things you can say in English when you meet someone you haven't seen in a long time.

Some greetings
Long time no see!
Wow! Haven't seen you in ages!
I don't believe it! It's…. (name of person)

Complimenting the other person
I hardly recognised you!
You look well!
You look great!

Some questions you can ask
How's life treating you?
What have you been up to recently?
Are you still in… (name of town)
How's …. (name of mutual friend)