Red = corrections; Blue = my notes

Playing basketball

It was really nice and warm, so I decided to play basketball with my friends. I haven't played it for three months. When I played in After playing for ten minutes, I felt my legs are were sore and I almost couldn't breathe (or, "I couldn't catch my breath") smoothly.I was thinking wondering whether I am too old now. But I guess I didn't work workout for a couple weeks, and I ate too much. My weight is going straight up. I'm a little afraid nowI am worried, so I make made a decision that to exercising exercise every day as far much as I can. There are many gyms in the America, especially on the post (I don't know what "post" means here) and also a lot of people working out in here. I like it, andhope I can lose some weight before I go back my country.

When you write, think about if the topic happened in the past, present, or future. For example, "I felt my legs are sore." This happened in the past, so you should write "I felt my legs were sore."

Your writing is pretty good, and even with the mistakes, most English speakers would understand what you meant.

Playing basketball

It was really nice and warm, so I decided to play (==> have a game of) basketball with my friends. I haven't played it for three months. When I played in ten minutes (During the first ten minutes of the game / Ten minutes into the game), I felt that my legs are were sore and I almost couldn't breathe smoothly properly. I was thinking whether I am old now it was due to my old age. But I guess the reason why was that I didn't work out (are you talking about exercising here?) for a couple weeks and ate too much. My weight is go straight up  is increasing. and I'm a little afraid now, so I make a decision that decided to exerciseing every day for as far much as I can. There are many gyms in the America, especially on the post (???) and also there are a lot of people working out in here there too. I like it and so hope I can lose some weight before I go back to my country.

(^^)v