"What have I come to, the high city of sand dunes?" What is the real meaning of the poem "Du Fu at the Sand Dune Gate"?

Send Du Fu down to Dune City

Lipper

What am I doing here? A city of sand dunes with high terrain.

There are ancient trees on the edge of the city, and autumn sounds ring day and night.

Lu wine is not drunk, so sing a song for nothing.

If you think of a gentleman, you will send him to the south.

translate

What brought me to this place? I have tasted the lonely and boring idle life. Since you left, the only things that accompany me every day and every night are the old trees on the edge of the city and the rustling of the bleak wind. How can a person be drunk when he is drinking thin wine? How can a person listen to Qi Song alone to relieve loneliness? My thoughts of you, like this mighty water, follow you south closely.