i got a call for an interview today, the employer asked for friday but i was busy so we decided for monday

does it look bad when you turn down the day they asked for or is this okay?

what do they employers assume? would they think i have other interviews(which i dont)

if i come in monday, should i say sorry about not being able to make it friday because of an appointment? or should i be honest and say its my best friends bday and i couldnt make it? will they like that?

did i lose respect? or do they understand?

should i call back and reschedule for friday or just leave it???????