Hi!I'm 19 y.o and have a problem which I want very badly to fix it but I don't know how.

My problem is that everytime I approach a girl I run out of things to say and it's fucking frustrating for me. My fear is not approaching girls, my fear is that I know that I will run out of things to say. My mind goes blank.I have this problem for a long time and I really wanna fix it. How to start?What challenges should I do? I'm willing to do whatever it takes to get rid of this problem but I don't know what to do.

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Also I can't get out of my head.I create all kind of scenarios is my head.Sometimes I think I'm crazy.

Give me some help, please.

Thanks!