# if I judge

Possible meanings are 1) "if I judge people" or 2) "whenever I judge people"

# my judgment is true

Possible meanings are 1) "my judgment will be right" or 2) "my judgment is right."

# I am not alone, but I am with the Father who sent me

Jesus, the Son of God, has authority because of his special relationship with his Father. 

# I am with the Father who sent me

"the Father who sent me also judges with me" or "the Father who sent me judges as I do"

# the Father

This refers to God the Father. It is best to translate “Father” with the same word that your language uses to refer to a human father.