Timeout (504) #50

When I upload a large file (e.g. 1.4 GB), I get a timeout (http 504) on one of the (post) requests. The file is completely uploaded and merged. However, the client does not know about it. On the client side, the transfer information ends with: progress:1, error:true, success: false, complete:true. The request is waiting for the response from the server. Maybe I can solve the problem by increasing some timeouts on the server side. However, I have already tried a lot without success. Would it be possible to flush something like a status from time to time on php side so that I don't run into the timeout?

Thanks for any advice.