en_tn_lite_do_not_use/act/09/20.md

Right away he began to preach

"he" refers to Saul

saying that he is the Son of God

"he" here refers to Jesus.

All who heard him

This is a hyperbole for "many who heard". If you express exaggeration differently then use your form. (See: rc://en/ta/man/translate/figs-hyperbole)

Is not this the man who destroyed those in Jerusalem who called on this name?

This is a rhetorical and negative question that is emphasizing Saul was indeed the man who was persecuting the believers. It can be stated as, "This is the man who destroyed those in Jerusalem who called on this name Jesus!" (See: rc://en/ta/man/translate/figs-rquestion)