I've been working with .NET desktop applications for the entirety of my career so far, and my current position is asking me to come up with training I'd like to spend some of our dev training budget on.

I'd like to start building much stronger backend and web development skills, I've done a few tiny toy projects with varying success (tiny frontend with Angular, unfinished larger frontend with React, tiny Web API with ASP.NET Core).

My manager agreed with that when we had our last 1:1 and also recommended learning C or C++ as well, since I'm self-taught and don't have that experience from college.

I believe we have access to the O'Reilly web collection, and I've already got a Pluralsight account through work, but my manager and director have talked about being open to other learning paths so long as they can be vetted. What are some recommendations the community might have based on my goals and known available resources?