Скачать или смотреть How to make a picture transparent in PowerPoint | Here are describing 3 Options

In PowerPoint, you can make a picture 50% transparent using the following steps:

Option 1: Using Shape Fill with Transparency
Insert a Shape:

Go to the Insert tab, select Shapes, and choose a rectangle (or any shape you like).
Draw the shape to cover the area where you want the picture to appear.
Fill the Shape with the Picture:

Right-click the shape and select Format Shape.
In the Format Shape pane, go to Fill Picture or Texture Fill.
Click Insert and choose the picture you want.
Adjust Transparency:

In the same pane, adjust the Transparency slider to 50%.
Option 2: Using Picture Transparency Tool
Insert the Picture:

Go to the Insert tab, select Pictures, and insert the desired picture.
Adjust Transparency:

Select the picture, then go to the Picture Format tab.
Click Transparency and choose one of the preset transparency options or click Picture Transparency Options.
In the Format Picture pane, adjust the Transparency slider to 50%.
Option 3: Manually Edit in an Image Editor
If PowerPoint does not meet your needs, you can use an image editor like Photoshop or Canva to make the picture 50% transparent and then insert it into PowerPoint.