This means: Allah is the greatest

Notes :

1- You should raise your hands with the takbeer. Look at the picture
2- Be careful: When you start to pray don't look at the sky because it is forbidden as the Prophet peace be upon him said :" People must refrain from looking up at the sky in prayer, or their sight will not return to them (and in one narration: or their sight will be plucked away)

Then .. you make Ruku' and say :

This means: How Perfect is my Lord, the Supreme!

Note :

Be careful:

The Prophet said : Verily, I have indeed been forbidden from reciting the Qur'aan in rukoo' or sujood. In the rukoo', therefore, glorify the Supremity of the Lord, Mighty and Sublime, in it; as for the sujood, exert yourselves in supplication in it, for it is most likely that you will be answered ...so it is forbidden to read Quran in Rukoo' or Sujood