Try to stick to one idea at a time. Giving someone a choice is important, but too many options can be confusing and frustrating.
If the person is finding it hard to understand, consider breaking down what you’re saying into smaller chunks so that it is more manageable.
Ask questions one at a time, and phrase them in a way that allows for a ‘yes’ or ‘no’ answer (eg rather than asking someone what they would like to do, ask if they would like to go for a walk) or in a way that gives the person a choice (eg ‘would you like tea or coffee?’).
Rephrase rather than repeat, if the person doesn’t understand what you’re saying. Use non-verbal communication to help (eg pointing at a picture of someone you are talking about).
If the person becomes tired easily, it may be better to opt for short, regular conversations.