The Yashica Electro 35 was a fixed-lens 35mm rangefinder film camera that gained tremendous popularity from its introduction in 1966 until at least the end of the 1970s. The lens is not interchangeable, but rather fixed solid to the camera body. The camera has a 45mm lens with an open aperture of f/1.7. You focus the camera by turning the focus ring on the lens while watching through the viewfinder. Two images of the same subject gradually come together until superimposed over each other. Taking the lens off the camera requires some delicate work.
Examine the front of the lens of the Yashica Electro 35 to make certain there are no dents in the filter ring or the black front of the lens. This will have the lens information imprinted upon it. Dents in either of these will make it harder to get the lens off, but if you add a bit of synthetic grease along the joining area between the black ring and the filter threading with your finger, it should make it a little easier.
Use the slotted spanner to get into either side of this black ring. Because this lens was not meant to be taken apart by anyone other than a professional camera repair person, it will be quite tight. Take your time, but apply sufficient force to pull this ring out.
Take hold of the entire front portion of the lens and twist it. The entire lens element group should unscrew relatively easily. In the filter ring, you will see three Phillips screws that you do not need to remove unless you want to disassemble the entire lens. If you do, for example, to replace the filter ring or lens elements, unscrew these screws.
Remove the three Phillips screws in the black ring to disengage the lens. When you remove these, you can lift out the rest of the lens, leaving behind the shutter circuitry and the shutter itself. At this point, you can replace the lens with another one by reversing these steps.
Although you may love your personal Yashica Electro 35 and want to replace just the lens if it malfunctions, you might need to do more work than just that. The shutter is a delicate electronic mechanism that takes skill to repair. You might want to consider replacing the entire camera---they are readily available in used camera shops and online websites---instead of just the lens.