how to change text in slide layer

hello I can not edit a text in a positive layer I thought that this layer had a grouped image and text box but this is not the case the menu is grayed out. the pointer remains continuously in shape has four arrows to move this layer but not to modify the text and yet this one is present it is underlined by a red wavy line.

it could be simple but I don't know where the menu is to have access to the text. This file is not my creation and I start without training with this software. if someone can tell me a way to follow or a method ...

Thank you

this picture perhaps help you to see what I mean

it's a slide view