# We all agree

"No one can deny"

# that the mystery of godliness is great

"that the truth that God has revealed is great"

# He was revealed ... up in glory

This is most likely a song or poem that Paul is quoting. If your language has a way of indicating that this is poetry you could use it here. Some modern translations read, "God was revealed" or "God appeared." If Paul is quoting a song or poem, the word "he" refers to Jesus Christ. If he is not quoting, the word "he" could refer to either God or Jesus Christ.

# in the flesh

"as a true human being" 

# was vindicated by the Spirit

"the Holy Spirit confirmed that he was who he said he was"

# was seen by angels

"the angels saw him" 

# was proclaimed among nations

"people in many nations told others about him" 

# was believed on in the world

"people in many parts of the world believed in him" 

# was taken up in glory

"God the Father took him up to heaven in glory". 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. This means he received power from God the Father and he is worthy of honor.