Understand the idea
Download speed describes throughput while latency describes response delay. A fast download test can coexist with delayed interactive responses.
Put it into practice
Run a reputable connection test, record both latency and throughput and compare results on the same network at another time.
Know the limits
A single speed-test result does not measure the performance of every website or server.
The wider context
Connection tests are most useful when they are repeatable. Compare similar conditions and record the time of a problem. Faster networking can improve responsiveness, but it cannot create reliable returns or change the rules of an online activity. Avoid tools that require unnecessary device access.
Your next step
Use the practical step above only where it fits your situation. Before an account-specific action, check the current instructions from the service or device provider involved. Write down what you observed and what remains uncertain; that makes a follow-up question more useful.