I'm tooling around looking for an answer to my own OpenVPN Question,cand saw this.
All I can do to give you hope is describe my experience.
I use OpenVPN to access my Synology NAS, and if my network at the remote end is good, I don't have anywhere near the problem you have. I recently switched to a provider that uses fiber (only recently became available) and both the up and down is 1G (I verified).
You might have configuration issues that throttle your throughput if you have 35Mb up speed. You won't be fast with that, but it shouldn't be excrutiating. I had 10Mb up, and that was excruciating.
How bad is it when you push a similar file up to the server? If it is not much faster, there's definitely something outside the encryption slowing you down.
It doesn't, so I use OpenVPN ony DSM when I remote connect, and use ExpressVPN on the devices that need it for anonymousness.