An umbrella

Yesterday, when I finished my work, it's was very late, and I found it was raining, became very cold outside. Lucky, I put an umbrella in my knapsack everyday. I think it's a good habit, aha!

"one, two, three...." I was counting the buses and hoped the next bus was the one that I was waiting for. A grandma and a grandchild came to the busstop when/as I was waiting for the bus, their hair was wet, so I let them stand under my umbrella. I thought it was must be uncomfortable to be without an umbrella on this cold day.

I knew that they got off at the different busstop from the conversation.
"Give it to them, you are so young."
-"Don't, keep it by yourself, or you will get cold!"
"Don't worry, you will be ok, they need your help!"
-"Don't, otherwise you need to spend extra money for an umbrella!"
.....
Two voices appeared in my ear to argue inside my head. I hesitated, give it or not?

But when I saw the old lady was as old as my mother, and the child was as young as my daughter, they reminded me of my family, then I had a decision, I gave my umbrella to the grandma and grandchild. :)
I hope if my mother and daughter without an umbrella on that day, someone could help them too.

Just a few stylistic changes, overall very well written, almost poetic!  I got lost with the conversational bit because I could not imagine the environment.  At first, I thought the two voices were fellow passengers waiting at the bus stop.

Nice gesture of kindness, by the way!