Participle pharases

e家教緊Participle pharases
我想問下點分幾時用present participle pharases同past participle pharases,,,

e.g.Since Evans came to this school, he became every girl's idol.
答:Since coming to this school, Since became every girl's idol.
咁點解會用present participle pharases???

e.g. Mr. Bliue is fired. He has to find a new job.
答:fired, Mr. Bliue has to find a new job.
咁點解會用past participle pharases???

thx:)