God.
If your question is referring to human beings, we believe the most in God's servant Moses (Numbers ch.12; Deuteronomy ch.34).
We believe in God.
Jews believe the Old Testament, but they don't believe most of the New. So yes they did.
The Hebrews had a covenant with God. Many Jews today still believe this (at least, in one form or another).
Some Jews are Christians but most are not. It is because Christians believe that Jesus is the son of God, the Messiah, who died as the lamb of God, a sacrifice for all who believe. Jews do not believe this.
Most Jews believe that Humans have free will, and that suffering is the result of bad choices on the part of those who cause the suffering.
Jews pray to God.
Jews believe in God. The word Yahweh, Jehovah, and all variations are Christian words that have never been used by Jews. In daily conversation most Jews use the name HaShem to refer to The Creator.
Ethnically Jewish people who are Christians or Messianic Jews. It is worth noting that most Jews consider Messianic Jews to be Christians.
It's the word
European Jews.
European Jews.
That depends when and by whom.