Movie version of Keynote file - adjusting display times

MacBook Pro (Retina, 13-inch, Early 2015) MacOS High Sierra. Keynote v.9.1

A colleague and I recently gave a presentation, which included a Keynote slideshow.

I separately filmed us speaking - but the slideshow was not part of the video recording. (not practical to do).

Each Keynote slide needed to be up for a different duration.

Some of the slides had “builds” (is this the right word?) and their durations also varied, depending on how long the information was referenced in the talk.

I want to create a movie of the talk - with the slides - where the focus is mainly on the slides, including an inserted frame (I don’t know the correct terminology) showing the speakers - ideally, occasionally expanding to take up the full picture.

In the real world of the presentation there were inevitable hesitations and a couple of “blips” in the speech.  I have gone through the video of the speech with iMovie and deleted these issues as far as possible and added transitions to conceal the jump.

However, the movie I’ve created for the Keynote slideshow (exported from Keynote) sets every transition for the same duration - and likewise for the builds.  It does not seem to permit any alternative.

This doesn’t fit with the timing of the speech movie!

I would like to organise the movie version of the keynote file to fit in (time-wise) to the pace of the movie of the speech - so that the slides coordinate with it.

Has anyone got any suggestions? I’m by no means an expert in working computers of any type, so my skills are limited. Any assistance will be sincerely appreciated!