What is the nationality behind the surname Alavanja?

Question:no one anwered my question

Best Answer - Chosen by Asker: no one anwered my question

Almost certainly it originated in Croatia, part of what was once called Yugoslavia. There is a village called Alavanja, in the county of Zadarska in Croatia. The seven countries that were once part of Yugoslavia are Bosnia and Herzegovina, Croatia, Kosovo, Macedonia, Montenegro, Serbia, and Slovenia. The surname can be be found in most if not all these countries, but the main concentration seems to be centred on Croatia.

spanish

the name appears on immigration lists as coming from places such as Yugoslavia, Croatia, etc. No indication that it is Spanish. If the young man was born in the US, his nationality is American.. his ancestry is another definition.
Your question was posted very late at night, not to mention that you are asking concerning another person. When you want information concerning someone else, it is normally a courtesy to ask them directly.