Your suggestions and advice arewere very useful
... the interview had already taken place.... so you need to keep this sentence in past tense.
I reached half an hour before the interview time and submitted my resume at the reception. After waiting for one hour
These sentences have no grammar issues. But they don't seem to contain much meaningful and useful information. Your prompt says;
Explain what happened at the interview.
.... but this needs to be the information regarding how you did fare at the interview, what did the panel ask you about, how his advice was helpful answering certain questions etc.