Repeat in the order bellow after each line of Athan, as it can be seen, only after 'Hai ya ala ssalah' and 'Hai ya ala alfalah' that you do not repeat the same (Say the Arabic- for a clearer picture):

Allah is the greatest Allah is the greatest
Allah is the greatest Allah is the greatest
I bear witness that none has the right to be worshipped except Allah I bear witness that none has the right to be worshipped except Allah
I bear witness that Muhammad is the Messenger of Allah I bear witness that Muhammad is the Messenger of Allah
There is no might nor power except with Allah There is no might nor power except with Allah
There is no might nor power except with Allah There is no might nor power except with Allah
The prayer is better than the sleep The prayer is better than the sleep (during fajr athan)
Allah is the greatest Allah is the greatest
None has the right to be worshipped except Allah

Note: (While hearing the athan) one should repeat just as the mu-aththin (one who calls to prayer) says, except when he says:

hayya 'Alas-salah (or) hayya 'Alal-falah which means “come to prayer, come to success” instead, one should say, “There is no might nor power except with Allah.”

allaahu akbar, allaahu akbar
allaahu akbar, allaahu akbar
ash-hadu an-laa ilaaha ill-allah
ash-hadu an-laa ilaaha ill-allah
ash-hadu anna muḥammadar-rasoolullaah
ash-hadu anna muḥammadar-rasoolullaah
laa ḥawla wa laa quwwata illaa billaah, laa ḥawla wa laa quwwata illaa billaah
laa ḥawla wa laa quwwata illaa billaah, laa ḥawla wa laa quwwata illaa billaah
aṣ-ṣalaatu khayrun minan-nawm, aṣ-ṣalaatu khayrun minan-nawm
allaahu akbar, allaahu akbar
laa ilaaha ill-allaah