There are several websites which offers you to download the subtitles of any movie in .srt or .sub format, like Opensubtitles.org Sometimes the subtitles are damaged or time shifted.

You can use Subtitle Modifier to edit and fix the subtitles. You also can create your own subtitles from this utility.

1- Click here to download

2- Install and launch it, and load any subtitle file.

3- Now you can

Add or Drop off a dialogue

Look out for the desired dialogue or time in this box and edit the text accordingly

Time Shift your Subtitle

Under Manual Modification you can add or subtract mili seconds for subtitle appearance adjustment, in case the subtitles are lagging or leaping, you can use frames as units of addition or subtraction instead of time, just select the Frames instead of Time (ms) After entering the value press the +or - button to add to subtract respectively. 

Split Subtitle

Click on Split subtitle and specify the time on which you want to split.

You can play around with other tools to get the best out of it.