One autumn afternoon, Peter strolled

[Bassim]

Have I made any mistakes?

One autumn afternoon, Peter strolled through the town and bumped into Tim, who he had not seen since their graduation, ten years ago. They hugged each other and shook hands, and as he held Tim's fleshy hand he wondered how he had let himself got so fat. He remembered him as lean as a rake. As if he could read his thoughts, Tim said, "Lucky you, mate, you didn't change at all. Look at me, as fat as a barrel."
"You probably eat too much sweets, and don't exercise much,"Peter said.
"It's my wife's fault." Tim said. "She is spoiling me with her food."
"Any children?" Peter asked.
"Two, a girl and a boy," Tim replied. "And you?"
"None. I'm not married either and don't have any plans for a marriage."
"I remember you telling me many years ago that you'd die alone like a wolf. I told you you were going to change when you got in love, but you assured me that would never happen."
"I like my freedom more than anything else," Peter said. "Any woman will feel alone beside me. She'll run away, thinking I was a loon."

 

[teechar]

One autumn afternoon, Peter strolled through the town and bumped [1] into Tim, who [2] he had not seen since their graduation, ten years ago [3]. They hugged each other and shook hands, and as he held Tim's fleshy hand, [STRIKE]he[/STRIKE] [4] wondered how he had let himself got [5] so fat. He remembered him as lean as a rake. As if he could read his thoughts, Tim said, "Lucky you, mate, you didn't change at all. Look at me, as fat as a barrel."
"You probably eat too much [6] sweets, and don't exercise much,"Peter said.
"It's my wife's fault." Tim said. "She is spoiling [1] me with her food."
"Any children?" Peter asked.
"Two, a girl and a boy," Tim replied. "And you?"
"None. I'm not married either and don't have any plans for a [7] marriage."
"I remember you telling me many years ago that you'd die alone like a wolf. I told you you were going to [8] change when you got [9] in love, but you assured me that would never happen."
"I like my freedom more than anything else," Peter said. "Any woman will feel alone beside me. She'll run away, thinking I was a loon."

1- Rethink the tenses.
2- Who is not wrong, but can you think of an alternative?
3- Do you know the difference between "ago" and "before"?
4- Do you know why we need to use "Peter" here instead of "he"?
5- I think you'll work out that one.
6- "Sweets" is a countable noun.
7- Do you know why "a" is wrong there?
8- You need another form.
9- We don't get in love.

 

[Bassim]

I believe the changes should be these.

1. 2. 3. Peter was strolling through the town and bumped into Tom, whom he had not seen since their graduation, ten years before. (I have read the rules about the use of "ago" and "before" but unfortunately still make mistakes).
4. I believe that it is clear from the text that it is Tom who is fat. We don't need to use "Peter." (Peter is holding Tom's fleshy hand, and then Tom says how fat he had become, while Peter didn't change at all. The text is written from Peter's point of view, so it clear who is fat. It is the second sentence that shows whose thoughts we hear.
5. how he had let himself get so fat
6. too many sweets
1. She spoils me with her food
8. 9. I told you you would change when you fall in love.
7. marriage. ( I believe "a" is wrong because we are talking about marriage in abstract terms).

 

[teechar]

Right.
About #4, I still think it's a good idea to insert "Peter" instead of that first "he", and I would in fact change the subsequent "he" to "Tim".

 

[Tarheel]

The word "whom" is going out of fashion, but some still cling to it.

Try:

Peter said, "Any woman would feel alone beside me. She'd run away thinking I was a loon."

I don't get the part about dying like a wolf. (Maybe you mean: like a lone wolf.