Hi m55
It sounds like Chrome's sluggish upload/download troubles aren't producing error messages of any kind? [If they have produced errors, let us know which errors].
I looked around, and it seems a fair number of Chrome users experienced issues similar to your starting about mid-October of 2015. Some of the tactics they used that proved effective for some of them:
1) Empty the Downloads folder that Chrome is using on your computer (you don't have to delete the data, just move it to another folder & save it that way).
2) If you changed the location of the Downloads folder that Chrome is using, try setting its location back to its default location.
3) Uninstall & reinstall Chrome.
4) Some users tried things using a different account, or simply not "logged in" to their account.
For testing purposes:
1) Try things with a different browser temporarily, to see if only Chrome is having the slowdown issues.
2) Test the speed of your Internet connection with Chrome, and then with another browser.
3) If your usual Internet speed has slowed tremendously, try "power-cycling" your modem/router/gateway device [power off the device - wait one minute - power on the device - wait about five minutes - test for connection speeds].
4) If you Internet connection speeds continue to struggle, call your provider, and have them test the signal strength to your device. And have them remotely test your device as well.
It goes without saying - that saving files requires room, so of course double check that free disk space isn't an issue on the drive where the downloads are stored.
Chrome has a few troubleshooting tips of its own - can't hurt to have a look at them (though most of them are for error-producing scenarios)
Fix file download errors in Google Chrome - Chrome Help
Let us know if none of the above helps.