A phone can be enough for introductory activities when the tool you choose supports it. You can practice asking clear questions, reviewing short explanations, or organizing non-sensitive notes. More complicated tasks may be easier on a larger screen, but that does not prevent a useful beginning.
Start with short material you can comfortably read and check. Review any voice transcription before submitting it, and confirm which app or website you are using. Choose an exercise that fits your device rather than measuring your progress against someone else's equipment.