Hello.I’m new here in the forum 
I’m 15 years old (probably one of the youngest blender users here)
I’m still a beginner and this is a test render.Any advices,opinions or suggestions will be welcomed
(I edited it a little bit in Photoshop)
I’ve been using Blender commercially since I was 15, it is a good age to start, my advice to you in Blender would be to keep going at it. The first time I used Blender was when I was 14, and I started my job in animation when I was 15, and honestly, if you keep at it, then that is the best advice I can give. I would also, if you have a spare 10 pounds or whatever, buy a Udemy course in Blender. They are roughly about 24-36 hours long, and are very informative.
As for the render the cupcakes are modelled good for a beginner, I assume you are using Cycles? I can’t see much noise, however, the material/texture you are using for the strawberry isn’t very strawberry-ish if that makes sense, it looks almost like a Rose Gold iPhone. You could also address the cupcake paper thing (can’t remember for the life of me what it is called), as they don’t appear like a normal one would if that makes sense.
Sorry if it felt like I was destroying your work, but constructive critisism is the best way to get better. If you ever need to ask a question, pm me or whatever and I would be more than happy to help you in any way you I can, as it will be easier for you to learn Blender at a younger age as you can learn things easier when you are younger.
If you don’t mind me asking, what do you intend on using Blender for as your end goal. Are you looking for game assets? Animation? What do you want to achieve?
But its nice that you know to do the post production composition (something I never used to do), and that can really help out your renders
I look forward to seeing your future work
Kind Regards
Benjamin Watts