Hello, Sandro. I read your work and I have enjoyed it so far. You have talent in writing and it's fairly well-written, but I have some nitpicks to point out and give you some suggestions to improve your writing.
First, it's the dialogue. You cannot write and merge the conversation between characters into a single paragraph. You're mixing and potentially confusing the readers in who-is-who is talking. You have to separate them individually. Like this:
"Hey, dude, you must be my new roommate!" he said with a warm voice. "I'm Jack, by the way." He held out his for me to shake.
I smiled and shook his hand. "Nice to meet you, Jack. I'm Sandro," I said, trying not to look too nervous.
Second, you are overusing the "I couldn't help but" a lot. In my opinion, it's getting pretty annoying.
Instead of: "It was a backhanded compliment, I knew, but I couldn't help but smile anyway."
Write this: "It was a backhanded compliment, I knew, but I smiled anyway."
Please, use less the "I couldn't help but" or drop it all together. I hope you will do better in the future.