How to improve in code after you know many languages?

How to improve in code after you know many languages?

Over the past years I learned about 14 programming languages (assembler
phyton delphi qbasic c++ c# ruby perl - etc etc etc). However this was all
out of my own interest, I didn't went to school for it.
Now without real education I am into a team with other programmers. We are
into robotics with our work. In contrast to me they know about 2 languages
and many frameworks I never had heard of before.
I don't really feel behind them, but they can surprise me and other times
I can surprise them with solutions. The largest difference is that they
have worked for years in the IT, while to me the programming part, is new
and I enjoy it. But after the many languages I find it a bit hard to
improve. Sometimes I see code (or tools) that are new to me.
I never used tools as anksvn, or did versioning or never had seen USB
driver made in code, I got used to them, learned from them on projects and
my colleagues. I started making money with code (without a real degree)
the last 2 years.
Given that I haven't found any good YouTube channel or a book, that might
improve my skills, how can I improve further?
My interests these days are C++ and C#. The point I loose interests if
books start with the basics of "if then while for types objects" after 14
languages you get that.