Removing text boxes from a video

Not automatically. You'll need to find a part of the video where the text box is the smallest, then export that frame as a Photoshop file using the Composition/Save Frame As/Photoshop Layers file, open the file, remove the text box, create a mask/matte so all you have is background (including the barbell, then create another layer with just the barbell. You then import that PSD as a composition and copy and paste the fixed background and the barbell into the main comp. Then, it's just a matter of positioning and editing the replacement layers on top of the original video. 

The project will probably take a new user about an hour. It might take about fifteen minutes if you are very familiar with After Effects and Photoshop.