Use a pair of tweezers to remove the loudspeaker, pivoting it up and out of the phone.

If the loudspeaker doesn't want to pivot up, try pushing it closer to the battery.

Before you install a replacement loudspeaker, check the adhesive gasket:

If it is in good condition, you can re-use the gasket. Make sure that the gasket does not cover the exit hole.

If the gasket is pulled out of place, remove it and replace the adhesive with a pre-cut strip or Tesa tape.