502 Bad Gateway nginx

Hi, I have a web app running with Forge on digital Ocean. I use Laravel Datatables for displaying multiple rows in a view. When I export the table (4k rows) to .xls after aprox. 1 minute I receive the error: 502 Bad Gateway. I read that I should change this nginx settings to: proxy_connect_timeout 300; proxy_read_timeout 300; but I don't know where to do that. Can anyone help me? By the way, this is happening also when i'm importing large datatables from csv.