It sounds like you're talking about pyramiding the weight up. This is usually done for strength training where it's important to keep increasing the load, and the lifter pyramids up to a top set. This isn't really necessary for hypertrophy, especially as a beginner. The most important thing for hypertrophy is getting your muscles 0-3 reps from failure with enough volume to stimulate growth. This can be done with the same weight over multiple sets.
And a related question... if you're doing straight sets with the same weight, should you get the same number of reps in every set? If you're training to failure, you will not be able to get the same number of reps in subsequent sets and that's okay. If you are leaving reps in the tank (you can still make good gains leaving 1 - 3 reps in the tank), you may well still get the same number of reps in subsequent sets, but it will feel harder.
It also depends on how much rest you're taking. The less you rest, the less reps you will get in subsequent sets. I highly recommend you take enough rest to maximise your later sets by getting more reps. Make sure you rest at least 2 minutes. Even 3 minutes is okay. The longer you rest the better actually from a "gains" point of view, but you just take much longer to complete your workout.
Another note... even though you are training hypertrophy, you need to increase the weight you can handle in the 8 - 12 rep range over time. If you don't, your gains will stop once your body has adapted to a certain weight. So if you hit your maximum rep goal in all your sets. increase the weight next time.
As for losing fat... All that matters is a calorie deficit. Cardio can help achieve that. Beginners can build muscle and lose fat at the same time, but keep in mind your muscle gains will be less while in a calorie deficit than what they would have been at maintenance or calorie surplus.
I hope this helped.