Adh-Dhariyat 51:56
وَمَا خَلَقْتُ ٱلْجِنَّ وَٱلْإِنسَ إِلَّا لِيَعْبُدُونِ
Wama khalaqtu aljinna wal-insailla liyaAAbudoon
"And I did not create the jinn and mankind except to worship Me."
Adh-Dhariyat 51:56, translation by Sahih International
A short reflection
I did not create the jinn and mankind except to worship Me. The one-line answer to why we are here.