I don't think this is really the right place to post this. However, I will try to help.
Toon Link's weakness is that when the opponent gets in (in other words, gets past his wall of projectiles), he get's comboed very hard or punished with a strong move. This means that against characters like Sonic and Mario, he sometimes struggles because they are both very good at getting close to their opponents and racking up damage. You may want to pick up a character with a good combo breaker or even a character that is good at getting in and performing combos themselves.