You've just boarded an airplane. Everyone is now on the plane, but people are still putting away their bags and other things. The flight attendant says:
All baggage must be stowed in the overhead container.
airplane, announcements, luggage, modal, 日本語サポート 
Your daughter is packing for a weekend vacation. She's packed two large suitcases and a backpack.You think that's too much. You say:
I find it hard to believe that you're really going to need all that luggage for just 3 days.
You're going on a trip with your friend. He's trying to get your suitcase into the trunk of his car, but there isn't enough room. He's pushing on it hard to try to fit it in, but you're afraid he'll break something. You say:
Don't try to force it in!
You're going on a trip with a group of friends. You're all riding in your friend's car. He's trying to put all the suitcases in the trunk, but yours isn't fitting. You think it might be possible to get them all in if they're all packed in the right way. You suggest:
Maybe if we rearrange some of this stuff...?
When you're looking for solutions to a problem, you can introduce different ideas that you have with "Maybe if...". For example, if someone is looking for a way to sell her old computer, you can suggest:
Well, maybe if you put it on Craigslist, someone might buy it.
In the example at top, the sentence doesn't include what the conclusion would be. Usually "if" sentences include the conclusion, but if the speaker and the listeners all know what the conclusion is, you can leave it off. In the original example, the conclusion is:
Maybe if we rearrange some of this stuff, we can fit all of the suitcases in the trunk.
But because everyone knows that this is what they're trying to do, it's not necessary to say it in the sentence.
To "rearrange" things means to change their order or position:
Did you rearrange the furniture in here?
I rearranged my schedule so that I could sleep in until 9:00 every morning.
You can also use the specific words "reorder" and "reposition". but "rearrange" can mean both of those.
"Stuff" can mean almost any physical items or material. It's similar to the word "things", but "things" are countable and "stuff" is not. So "stuff" is better to use when you're talking about a group of things that are different from each other - different sizes, shapes, etc.
"Stuff" is especially used to refer to things that you buy or own:
There's a good chance that you'll end up buying a lot of stuff while you're there.
Excuse me. Would you mind watching over my stuff for me for just a minute?
You're going on a vacation with two of your friends. You're riding in your friend's car. He's putting suitcases in the trunk of his car, but there doesn't seem to be enough space. You're not sure if your suitcase will fit in there with all the others. You ask:
Can you squeeze one more in there?
You're going on a trip to a foreign country for a few weeks. You're packing for the trip while your roommate helps you. You don't want to pack a lot of clothes because you want to be able to travel easily. You explain what you want to your roommate:
I'm trying to pack light.
luggage, progressive aspect, travel 