One common C++ coding practice is to prefer non-member non-friend functions to member functions. This is a great way to increase encapsulation and keep class interfaces as minimal as possible. When you type a dot . or an arrow -> after an expression, free functions that accept the expression as the first parameter will be suggested in the completion list after member functions:
You can clear this checkbox if you do not want to have free functions in the completion suggestions.
Show import items in basic completion
When a symbol that you want to use is not imported in the current file with the corresponding #include, but it is defined in the standard libraries or elsewhere in your solution, you can press Ctrl+Alt+Space to quickly find this symbol in completion suggestions: You can use this option to include import symbol suggestions into the suggestion lists of automatic and basic completion. Note that this comes with a performance hit (since each time when ReSharper builds a completion list, it has to look at all the symbols in the solution to match them), so it is disabled by default.