Remove words from a video without losing synchronization

[xugmu]

I'm trying to remove words from a video, for example: if the video says "good dog doesn't bark" I want it to say for example "good dog barks", the first option would be to introduce a silence (" doesn't " would be silenced) and the second would be to introduce a silence and then move "good dog" forward.
I've done it with an audio editor and it works fine but in the end the export came out out of sync with the video.
I think that, although it is complicated to do, it could be a good option for subtitle editing in the future.