Does "감사해요" mean anything? Does this mean "thank you" or is it an unnatural sentence?

How do I say these sentences in Korean? Hello, there are some phrases I would like to know, please! "I want to be fluent in Korean." "You are lying." "It's contagious." "I'm thirsty." "Give me that" or "Hand me that" "Who said you could do that?" "Don't you think that's a bit much?" "Listen." "Can you speak English?" "I want to get better."

How do I change 존댓말 to 반말? I can tell the difference between informal and formal speech when listening and reading, but I don't know how to convert sentences back and forth between them. How do you make a sentence informal? Likewise, how would you make an informal sentence formal again? Thank you for your help!

안녕하세요! 나의 친구에게 : 어떻게 지내세요? 잘 지내요. 오늘 한국어를 공부했어요. 이 책은 찾았어요. 나는 한국어를 조금 할 수 있어요. 그래서 공부할까요. 한국어를 다 할 수 하고 싶어요. 열심히 하겠습니다. 기대해주세요!

What is the difference between "처럼" and "같이"? I see and hear these terms a lot in songs and shows. How do I know when to use "처럼" and when to use "같이"? Are they interchangeable?