Gratz on your placement, benaji =) I'm sure you'll understand those difficult MUs soon
I really didn't play too many falcos. Because of the large amounts of people, was kinda hard to get friendlies with specific people in. That's why I can't really say much about approaches on falco, because I don't really know how the top level will handle it yet.
Falco: the CG is bad, but isn't what makes the matchup very difficult. Getting close is, though. Lasers aren't hard to shield/powershield because the timing is usually the same. The key to doing well vs falco IMO is definitely bthrow to dash attack. It's an immediate offstage. Try not to use fair much in this matchup, too. Nair is much better.
Sonic:
Shielding is not good vs him. You would want to jab sonic's spindashes. It works very well. Actually, you can jab most of what sonic does if he's just running around you. The thing that makes sonic scary is his ability to get close very fast as well as powershield and punish well-spaced attacks. Try not to space with fair in this match, too. I just did a lot of running shield dashes away and pivot jabs (and occasional grab), really. Don't worry about trying to kill him early, but just keep trying to shut him down and not get caught up in reads.