Your package is probably lost man.

I mail letters to UK and it takes 5-6 days.

Your friend could have gone to the post office and asked for
ground mail and it would be extra slow but should still be there
within 3 weeks.

Ground mail is stupid. You have to go to the post office and request
ground mail delivery and it only saves you about 20% on the price but
the delivery takes about 3 weeks.