Greek Scholars, questions

[Archaea]

Is there a root connection between pisteuo, which I translate as to believe, and epistamai?

And the difference between epistamai and gignosko and oida?

I'm also confused by the optative. It seems similar to German or French subjunctive, but Greek has subjunctive in a different sense.

And are most optative verbs first or second aorist?

If I wish to read a simple Platonic verse, where should I start?

I'm enjoying Homer and John, but wonder what else is out there of merit.