Do you think that maybe for me it might be better to go back to using my old camera , the Canon Power Shot A 720 IS ?
Welcome to the forum. It sounds like you need a higher shutter speed to stop the images becoming blurry. The general rule is 1 / (focal length 35mm equivalent). As the Nikon Coolpix L810 has a maximum focal length of 585mm as the 35mm equivalent your shutter speed should be at least 1/640th of a second.
I don't know if you have any manual controls on the camera. One way to get a higher shutter speed is by putting the camera into a higher ISO.
Another way to get sharper images is by stabilising your camera. At these focal lengths it's very difficult to keep the camera still. You can stabilise the camera by putting it on a wall, a table, ... Anything that keeps the camera still. You might want to consider using a tripod when you use the maximum focal length.
See if you can increase the shutter speed or stabilise the camera and if it resolves the problem with the blurry photos.