My friend is going to travel to another country
for few days and he will come back.
Is better to say for him:
1-Have a nice trip.
2-Have a nice journey.
For me, "Have a nice trip" means "Enjoy your holiday/vacation". "Have a nice journey" means "Enjoy travelling to your destination" but it doesn't necessarily wish the person a happy holiday/vacation.
You take a journey in order to arrive at the destination for your trip.
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.