"Δεν μπορώ να τρέξω!"
Translation:I cannot run!
Yes, in general this is my only complaint about this program: verbs are the most important part of any language, but the proportion of nouns, adjectives and pronouns to verbs on this program does not reflect their relative importance and their relative difficulty (and therefore time required for mastery) in the language.
Using the aorist stem (e.g. τρεξ-) indicates a single action, while using the present stem (e.g. τρεχ-) indicates a repeated, habitual, or continuous action.
You will see the same in the past tense (aorist for single events, imperfect for repeated, habitual, or continuous action).
Yes there is: να τρέχω is "to be running" while να τρέξω is "to run". I don't see why both are accepted interchangeably; I report them. (Sorry, contributors! :) Is it possible, in EN, to say "to run" and, with the right context, express some continuous aspect? It's not obvious to me; I think the continuous and non continuous tenses in this case match pretty well.
English uses the present simple tense for repeated or habitual actions, and I think such a simple tense would be appropriate for this sort of thing as well.
So things such as "He refuses to help me" are ambiguous between helping once and helping regularly or continually.
Or "Don't tell me what to do" could be either a one-time warning (Μη μου πεις [τώρα] τί να κάνω) or a complaint about many instances of speaking (Μη μου λες [συνέχεια/πάντα] τί να κάνω).
That's true, your examples are very helpful. But it's not really a present tense, it's the EN infinitive being compared with the GR subjunctive... I guess we need to keep an open mind about the possibilities! (But, as it is, I am trying to guess correct answers that may be missing from the database so I'll be reporting those cases!! ;)