Can't upload my zip, error 504

Hey,

just trying to upload my first project here (unreal engine assets pack as zip) but when reaching the 100% processing step I always get an error 504 message after 30-60 seconds. I noticed after reload the upload page I see the zip under files but I am not sure if this correct (uploaded correctly?) or not. What could be the problem? The zip is 3,7 GB and file name has no special characters (using _ though, 29 characters total)

Thanks.