I know C++ 2003 How to start learning C++ 2017?

I had a similar problem 8/9 years ago, but with C++11.

The trick is that there is no trick. You simply sit and use the feature you want to use. Besides that it is also beneficial to know C++14 before getting into C++17 and know C++11 before getting familiar with C++14 features. (Obviously prerequisite for C++11 is C++03/98, but that's already covered by OP).

If getting up-to-date with C++17 (C++20 actually was vote in 2020) I would start with feature list grouped here. The problem is that there are so many of them that one may have problems in how to approach them, thus I've provided an ordered list that shows how I would teach it to people:

C++11 warm-up

• nullptr - you won't be using NULL of 0 for null pointers anymore
• static assertions - allows you to enforce some assertions at compile time
• scoped enums - no more enums collisions!
• type alias

Basic C++11 stuff

• move semantics (overview + SO question) - move semantics and rvalue references are the corner stone of modern C++, what follows is the rule of 5 (or 3/5/0 if being precise)
  • rvalue references
  • move semantics in a class
  • rule of 3/5/0
• auto
• lambda expressions
• ranged for loops - because for(auto const& e: {1, 2, 3}) { std::cout <<e <<'n'; } is so cool :)
• classes related stuff:
  • default functions/methods
  • deleted functions/methods
  • final keyword
• constexpr specifier
• initializers lists - it is used mainly in std::vector<...> so it's important to know how it works and what are problems involved with them (it is not my favourite C++11 feature)

Extra C++11 stuff

• std::tuple
  • But avoid std::tie, prefer structured bindings from C++17 (you can break the rule here and look them up ahead)
• std::thread - no more pthreads!
  • std::ref - useful when you want to pass references to other threads
• variadic templates
• forwarding references - useful when want to preserve move semantics when dealing with templates

C++14 & C++17

• After these basics I would read about the other C++11 related features or moved to C++14 features listed here (and consult C++11 features list when necessary). Note that C++14 was a nice little amendment to C++11 so there aren't many new (and cool) stuff.
• C++17 features worth mentioning (very subjective opinion, at this point you should already know what you want/need to know):
  • inline variables
  • structured bindings
  • if constexpr
  • fold expressions 1 and fold expressions 2
  • lambda this capture changes/updates
  • std::variant + std::optional

C++20

• Concepts are the new big thing
• immediate functions
• IMHO modules will be a dead end as long as C++ will be split into header and implementation fiels (besides Rust have better package/modules concept). But that's just an opinion bouncing in my head.
• Remaining C++20 and previous version stuff (obviously only a fraction was covered in this post :)).