# 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 is an important title for God. If your language must state whose Father this is, you could say "my Father" since Jesus switches to that in the following verses.