I shared some stuff I do to clean up and prepare a book before import to lingQ in the thread here. Problems with epub imports pushing words together - #10 by Hsingh
Hopefully some of the fixes/plugin work for you.
Unfortunately all these attempts to fix the book can consume a lot of time which could be spent learning. Sometime I have to import 2-3 times before a book imports the way I want it to. Hopefully LingQ sort out all the problems soon or at least create a guide on how to prepare a perfect ePub for import.