Desktop app ?

Nvm I'm stupid, and it depends what software you want to make.

I want to make an app with the ability of receiving informations from the web, with a good looking customization (flat design) and coding for math calculs like generating random numbers or the classics operators + - * / ...

You can use nodejs, javascript to make a desktop app using githubs electron

These days webapps are pretty good to offer almost desktop functionality but if you want to interact with your files locally then you better choose JDK. You will find Titanium useful if you are not ready to learn an new environment and want to develop using HTML/CSS/JS.

What is the best software for making a desktop app with these three languages ?

c# bro + asp .net

Use Electron for desktop app. popcorntime and discord uses electron

I am using Electron.js. With it, you can create very functional applications. Electron is evolving and you can always find the answer on the Internet. In addition, companies such as Microsoft use it.

Electron is good but you will need to know Javascript and understand how to use their RPC