Select the section you want to keep, press enter and read!
Activate the app by clicking on the icon, it becomes red.
Once it is activated, select the area you want to keep by clicking on an element, click on the same one to select the container of this element, click again to select the container of the container and so on. Click until you have selected the area you want to keep.
Then press Enter and it keeps only the highlighted area, the rest is trimmed!
To go back to the original version, click on the app icon, it will reload the tab.
Keep in mind that, it removes elements from the page and some interactive features might not be available.