I have a WinForms application which I want to translate into multiple languages. However, I do not have any experience with localizing a WinForms a
I dont have a solution for your first and second requirement but keep in mind that localizing a form is not as simple as translating each word. You need to check that each translated text fits in their respective control. Also, maybe you have an icon or an image which need to be change in another culture.
For your point three, you can change the language manually with the following lines:
CultureInfo ci = new CultureInfo("fr");
Thread.CurrentThread.CurrentUICulture = ci;