Every time I apply a master page on a left page the text box and everything in it displace. Is there an easy and fast way to fix it? This file has +300 pages so it would be nice to fix it automatically.
First, check your master/parent pages to make sure both left and right parent pages have the text frame properly placed.
If so, turn on Layout > Margins and Columns: Adjust Layout and move the frame.
If you are using Primary text frames AND the text is one long flow (or a series of long flows), delete all but the first page of each flow. The pages should be added in according to your preferences and the parent pages.
If your document only contains the main flow text frames (and no misc. frames), create an object style for the correct position frame with the Size and Position Options. Do a find and change for text frames and change to the object style. (Warning: if you have other text frames in this document, it will change the size of them too.)