en_tn_lite_do_not_use/act/19/04.md

the baptism of repentance

You can translate the abstract noun "repentance" as the verb "repent." Alternate translation: "the baptism that people requested when they wanted to repent" (See: rc://en/ta/man/jit/figs-abstractnouns)

the one who would come

Here "the one" refers to Jesus.

come after him

This means to come after John the Baptist in time and not following after him physically.