Please tell me my grammar mistakes.

It was raining today, but I forgot to bring my umbrella. After school I went to my dormitory to get my umbrella. Luckily the elevator door was about to close in a few seconds when I got out of my room door. Using the fastest speed I can I press the button “down”. The girl who was standing there was very stunned at my action. I thought I was a little bit rude. Then I blushed and said sorry to her.