Man's got a point / be there for her / happen / you know how /
Excuse me for asking many questions in one posting. I can only post twice a day.
I am studying Friends S1E24 script.

1. In the episode, Joey is taking part in a fertility test. Monica responses to Joey's line like this.
Joey: What, you think I'm gonna tell a girl I like that I'm also seeing a cup?
Monica: Man's got a point

How should I understand Monica's line?

2. This is from another Joey and Monica's talk.

Monica: Have you ever thought about being there for her?
Joey: What do you mean?
Monica: You know, just be there for her

Joey does not understand "be there for her" part, and neither do I.

3. I dont clearly understand Joey's this saying to Chandler:
"You know how you always think you're great in bed?"
Is it like "do you know how to be always great in bed"?

4. "Happen" is tricky to understand. Am I right if I think like these?
"It happens my room is very close to the parade route"
coincidentally my room~

"He happens to be a very nice guy"
he turn out to be~

Thank you

Question

Man's got a point / be there for her / happen / you know how /
Excuse me for asking many questions in one posting. I can only post twice a day.
I am studying Friends S1E24 script.

1. In the episode, Joey is taking part in a fertility test. Monica responses to Joey's line like this.
Joey: What, you think I'm gonna tell a girl I like that I'm also seeing a cup?
Monica: Man's got a point

How should I understand Monica's line?

2. This is from another Joey and Monica's talk.

Monica: Have you ever thought about being there for her?
Joey: What do you mean?
Monica: You know, just be there for her

Joey does not understand "be there for her" part, and neither do I.

3. I dont clearly understand Joey's this saying to Chandler:
"You know how you always think you're great in bed?"
Is it like "do you know how to be always great in bed"?

4. "Happen" is tricky to understand. Am I right if I think like these?
"It happens my room is very close to the parade route"
>> coincidentally my room~

"He happens to be a very nice guy"
>> he turn out to be~

Thank you

Answer

I will try to answer your questions the best that I can.
1) The phrase "you've got a point" just means that the person you are speaking to has a logical argument or a valid opinion. It is a way to concede an argument or agree with the other person. 
2) "Being there" for someone is an expression to mean that you are physically or emotionally available to help someone. You can be there for someone during their time of need, be there for someone emotionally, it means to support someone. 
3) Joey is saying, you know how you think this thing (that you are always good in bed)? It is a humorous expression implying that Chandler's thinking is incorrect and that he is, in fact, not always good in bed. 
4) You are correct on these last two parts. Those are a good way to understand those phrases.

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