Retime speed on subtitles

Is there a way to collectively increase the length of the clips of every subtitle as if i would retime and speed it?
sometimes the speaker is talking slow or to fast and the client asks to slow him or speed him up accordingly.
the question is - is there a way to also retime and speed subtitle clips or normal text clips?
sometimes the speaker is talking slow or to fast and the client asks to slow him or speed him up accordingly.
the question is - is there a way to also retime and speed subtitle clips or normal text clips?