I've had a look and found a helpful website by "Schengen Visa Info" regarding "How to Write an Appeal Letter for Schengen Visa Refusal": https://www.schengenvisainfo.com/news/how-to-write-appeal-letter-visa-refusal/
As they state on the website:
"...if you think that your first application was correct, and the decision on its refusal was a mistake, you can always appeal the rejection.
Article 32(3) of the Visa Code of the Schengen Agreement clearly states that those who have been refused a visa shall have the right to appeal."
The website even includes a sample letter and explains what documents you will need to hand in with your appeal letter.
As I understand it, visa applications get rejected if the authorities find the documents you handed in to demonstrate the purpose of your travels/ stay insufficient. Re-checking your initial application can help to back up the reasons why you intend to visit the Schengen area.
Here, the visa information site lists 12 reasons why an application may have been rejected: https://www.schengenvisainfo.com/news/common-reasons-visa-applications-get-rejected/
I hope this helps. Feel free to reach out to us again if you have any more questions!
Also, please remember to change your username in order to avoid confusion (see the comment I posted above).
All the best,