Learn design patterns or masterize .NET ? Please advice from experianced developers

I am wondering if it is better for me right now to learn design patterns right now or masterize .NET skills.

I am 2-3 years .NET commercially experienced. I know C# quite ok and sligthly WPF, MVC, etc. because I am working in some other API for UI.

In the future I would like to develop my own complex applications which could be desktop or mobile as well online.

I am still reading a lot to decide if I want to stick with .NET, and I am not sure yet. Python looks great for me too. Probably this decision would be taken later, in some years and now I would continue with .NET. So I have dilemma to learn design patterns (which are not linked to any language - are abstract) or go for .NET certification and focus on the knowledge they require to get them.

Also an additional question is if someone can recommend some materials and books about application architectures topic that refers to securities. For example I would like to learn how to design password storage mechanism, what do avoid in designing the model etc.