Your familiarity with the following is quite necessary to start learning Flutter. ... You should know Dart programming before you can learn Flutter: but that's easy too. Dart is Google's general-purpose programming language.

Do I need to learn Dart to use Flutter?

Do I have to learn Dart before starting learning Flutter? No. Dart is easy and purposefully similar to java/JS/c#. If you know one of these, you won't be lost here.

Which should I learn first Dart or Flutter?

I would recommend you to do a video course which would cover both Dart and Flutter at the same time as this one in Udemy: Learn Flutter & Dart to Build iOS and Android Apps. But I would strongly suggest you read the entire Dart Documentation from beginning to the end.