en_tn_condensed/act/18/25.md

Apollos had been instructed in the teachings of the Lord

This can be stated in active form. Alternate translation: "Other believers had taught Apollos how the Lord Jesus wanted people to live" (See: rc://en/ta/man/translate/figs-activepassive)

Being fervent in spirit

Here "spirit" refers to the entire person of Apollos. Alternate translation: "Being very enthusiastic" (See: rc://en/ta/man/translate/figs-synecdoche)

the baptism of John

"The baptism that John performed." This is comparing John's baptism which was with water to Jesus' baptism which is with the Holy Spirit.