After translating the captions and viewing your youTube video, if you see that the subtitles lines overlap eachother, it means that the original captions do not have the correct timings set.

Edit your original captions and set the correct timings. For example, the original captions can have these lines:

00:01 Hello

00:04 What are you doing

00:02 Hey there

As you can see, line 3 starts before line 2. Make sure this does not happen. Correct the entire caption then go back to captionizer, re-read the original captions and translate them again.