Why "way" is used in here? I think it is okay even though if it is not in here.

What is the difference between “do it” and “punch it” here?

"Punch it" here means "punch it in" or "send it". So it is just another way to say "do it". However, "punch it" is not a very common expression to use when using it to refer to doing something.

What is “windshield”? Is it only used to car? Is there any other word to replace this word?

A windshield is the glass window in the front of the car and in the back of the car. Typically, the word "windshield" is only used for a vehicle. Another word that can be used is window.

What does "what" refer to here?

"What" in this sentence means "the thing that..." It is being used as a pronoun in this sentence and refers to the concept of what Ross thinks is unagi. Here are example sentences of "what" being used as "the thing that." Ex: I don't know what I have in that box. Ex: It's what I like to call fun. Ex: I will tell you what I want to do tonight, I want to sing karaoke!

What does "stand watch" mean? How does this two verb come in a row?

To "stand watch" means to stand in a position and guard or watch someone or something in order to look for possible danger and or threats. Ex: There's a soldier standing watch by the door. Ex: Okay. Stand watch and let me know when mom arrives.

What's "put an end to" mean?

To "put an end to [something/someone]" means to cause someone or something to stop or to prevent something from continuing. Here, she means that she'll stop them from getting the good ending and result they want. Ex: I'm going to put an end to this misbehavior by contacting the kids' parents. Ex: They came up with a solution to put an end to the injustice.