According to my basic understanding of greek language at this time, you can drop all the pronouns. The greek people will know who is doing the action from the verb ending. However, if you wish to emphasise that particularly someone is doing that action you can keep the pronoun.
as in italian, spanish (and french?) the pronoun can, indeed, be dropped.
Modern Greek doesn't have "sh" or "zh" sounds (as in "mesh" or "pleasure"), so Greeks don't have to be careful not to let their "s" and "z" sounds be confused with them.
As a result, the "s" and "z" sounds can be pronounced a bit further back or a bit further forward without confusion, and the pronunciation and "wander" into the space that sounds like "sh/zh" to an English speaker. (Though not usually, I think, quite as far as a "typical" sh/zh sound in English.)
So you will definitely hear Greeks using sounds that sound like sh/zh to you.
For a learner, I'd recommend sticking with a "typical" s/z pronunciation at first.
Once you're more fluent and been around native speakers for a while, you can tweak your pronunciation a little if you wish.
When there's no context, as in the exercise, you can translate it either way. When there's context, it will be the same type of context you see in English, e.g. κάθε μέρα = every day (use simple present) or τώρα = now (use present continuous). Since Greek only has one present tense, we're not too worried about adding clues because we simply don't differentiate between the two meanings. Usually the situation is clear enough by itself and if someone is wondering about specifics they'll ask for a clarification.