GIVE ANSWERS - English

In the U.S. the phrase is "be on the same wavelength", the meaning is to agree or share a similar feeling about something. A similar phrase is "be on the same page", which seems to me to be a much more common phrase. Examples: "I really think we are on the same wavelength about this new project" or "I just wanna be sure we're on the same page". Hope this helps.

I feel on the same wavelenth, what does it mean?

In French, this is exactely the same expression : "se sentir sur la même longueur d'onde", that's to say, really feel connected.