Hi @didikpri,
Thanks for reaching out to us! While we do not hold an official rewards program for translators we sometimes give discount coupons (for renewals if you hold a license) to high volume translators (this means you should make a considerable dent).
You can take a look at our current translation projects for premium plugins: http://translations.theeventscalendar.com/projects. You’ll also find the links to the free plugins translation page.
Please let me know if this answers your question,
Best,
Nico