Márk Pap
It would be great if the tunnel region could be selected, because there are some ISPs that don't work well with Cloudflare, but changing the region would likely solve the issue.
Links:
https://www.reddit.com/r/selfhosted/comments/1gxby5m/cloudflare_tunnels_ridiculously_slow/
https://community.cloudflare.com/t/connection-to-cf-via-german-telekom-is-very-slow/656849/15