I want to get into windows, mac etc. development. So what program is good for making a program like for example paint or any simple program for windows

On Windows pretty much .net with windows forms

VB.Net if you like writing english sentences and not go too much into advanced features - C# if you want the more advanced features, imho microsoft loves C# more the recent years.

IDE: Visual Studio Community. Newest available.
Language: C#
API: WPF.
Don't go into Windows Forms. WPF is more customizable and feels better IMHO.

@Agred is it possible to use Java? I'm learning it now and I really like it

@Koppaster Technically it is possible but obviously with another IDE and API. Although I wouldn't recommend trying to write desktop apps with Java as a first project. If you want Java and UI maybe try Android?

@Agred Yea I started learning Java for android, but

I would like to try to create something for windows so I will probably learn c# too. Do you know what is the best way to learn c# at home?

@Koppaster if you want to learn C# and WPF then try out courses on Udemy. There should still be one of those discounts they do almost every month. You'll also need something on C#, but those two will probably be in one course so you won't have to pay for two courses separately.
If you'd rather stick with Java you have to choose between JavaFX, Swing or something like that.

@Agred Ok thanks a lot

@Koppaster Maybe check out SoloLearn to grasp C# basics. It's free.

@Agredi I got it today😀