How to use good "good luck "
good luck i know the original meaning hope you savety ,such as when you have a trip,your friends say "good luck",hope you back safety.
But i don't know "good luck "is that have bad meaning?Such as :you love a girl,you want to become his boyfriend and you told you friend this things,so you friends said"good luck"(they said very deeply and sound very good ),so in this situation "good luck “ is that means you will never pursue her?

Question

How  to use good  "good luck "
good luck i know the original meaning hope you savety ,such as when you have a trip,your friends say "good luck",hope you back safety.
But i don't know "good luck "is that have bad meaning?Such as :you love a girl,you want to become his boyfriend  and you told you friend this things,so you friends said"good luck"(they said very deeply and sound very good ),so in this situation "good luck “ is that means you will never pursue her?

Answer

Linda, 'good luck' doesn't usually have a negative meaning. But a person can say it to *express doubt* that you will achieve your goal(s).

A: I love Charlize Theron. I want to marry her.
B: Good luck. She hasn't been in a relationship in five years.

Person B expresses their doubt that what A says will come true.

Of course, if someone does not like you they can say just about anything to you in a negative way.

Answer

Yes, the expression could be used in a sarcastic way. Context and vocal cues will transmit the intended meaning. Someone might also say, "Lots of luck (on that)".  The message is that prospects of something coming to fruition are not good.