Progressive slowing down or speeding up of the sound synchronised with the video

Hello everyone,

I have searched the forum but I can't find a real answer as I need slow motion sound synchronised with my video. If I reduce the speed via Crtl+R, the sound decreases in the right way but it doesn't do a progressive curve. And when I switch to progressive mode using the pen tool (P key) to edit the slow motion curves, the audio doesn't slow down with the video, it's still the original sound.

Do you know how to synchronize the video with the audio for a smooth slowdown/acceleration?

Thanks in advance and sorry for my vocabulary, feel free to ask me to clarify  🥺