Tor is only as fast as the next hops and endpoint, meaning the slowest node is your max possible speed. It has nothing to do with YOUR connection speeds.
Example: if you have 1Gbps, but your next hop only does 20Mbps, and the next hop 10Mbps, and endpoint 1Gbps, the max speed you will get is still only 10Mbps because that is the slowest node in the connection chain.