correct form of the verbs

Henry lives in a small village. He (helps) the villagers collect letters at the post
office in town.
One day, he (went) to the post office and (found) on the shelf a big parcel for old
Mrs Tam. Henry (thought) that it (was) too heavy for Mrs Tam to collect if for
herself. Therefore, he (put) the big parcel on his bicycle and (rode) back
home. The next day, whe he (was knocking) on Mrs Tam's door, a big fierce dog
(run) out from the back of the house and (tried) to attack him. It (tore) his
trousers. Henry was afraid and (climbed) up a tree. A minute later, Mrs Tam
(came) out from the house. She (said) loudly to Henry, are you blind? I ( have put)
up a sign here for two days!
'(Do not worry), Mrs Tam. This (will not happen) again,' (replied) Henry.
Since then Mrs Tam (had not received) any letters from her friends. Henry never
(got) letters for her again.

2) preposition
Last Sunday, I travelled (by) MTR (from) Hong Kong to Kowloon. It was about
soon. After I got (on) the MTR at Kowloon, I found that my purse was
missing. I was sure that I must have left it behind (off) the MTR. I hoped
someone might find it (on) the seat and took it (to) the office (of) the MTR
station. I ran (toward) to MTR (at) once and hoped that I could get (back) my
purse.