It's "true" only if it exists in reality. Because you wrote it, it is fictional and didn't actually happen. So therefore it is not "true". If you are asking about any mistakes, then you need to ask, "Is this correct?" It still contains some errors and awkward phrases. Young has made a lot of good corrections, but you need to post longer texts in Notebook to get proper corrections and notes: http://www.italki.com/notebook

Sam: Dave, I’m worried about the team. Dave: But why? You have won every game since *Summer. Sam: Yeah, I know. We have practiced so much but still, I think that it is *still* not enough. Dave: How long have you *been practicing*? Sam: We have *been practicing* since Monday. (they still practicing right? Only if they stop practice then you can use past tense here) Dave: Don’t worry then, *that should be* enough. Sam: There is one more problem: Colin. Dave: The big guy? How long has he played in your team? Sam: He has played for five months. He usually scores most of our scores but he has been really late for weeks. When I *tried* to talk to him, he refused* to listen to what I say. Dave: Well, tell him *that* he can’t play if he doesn’t listen to you. Sam: I guess I’ll have to. I don’t like it. I have tried to talk with him since Monday but this time I hope he will listen to me. Dave: I hope.