Adjust syntax to be closer to Greek prose

[colder-is-better]

• The prose can be slightly adjusted to be closer to actual written (or spoken) Greek
• "Νόμισμα" in Greek means "coin", and for cryptocurrencies the actual English names are used. We should replace "Νόμισμα" for "Monero".
• In Greek, when people refer to GitHub issues they actually use English. We should replace "δημιουργήστε ένα θέμα" for "δημιουργήστε ένα issue".