Welcome, bienvenue, to the forum, this is a nice start. One thing - you would make it a lot easier for folks to review your images if you number them when you post them.
First impressions: First one) This is a little overexposed as the white part of the flower is blown out. Also, watch the crop, as you have cropped off the bottom part of the flower and this is not always a good thing to do.
Second one) This is a nice shot of this flower as you can see some detail in the petals of the flower. The only thing is the out of focus flowers in the background tend to be a bit distracting. You would have been better off, in my opinion, to isolate just the one flower against the green background and ensure that it is in very sharp focus.
Third one) Not too bad, but again the detail of the white flowers are blown out. This is going to be a problem when you photograph light flowers against a dark background, or dark flowers against a very light background.
When you are shooting a white flower against a darker background, such as you did in the first and third images, you have to remember that your camera's meter tries to turn everything into 18% grey, so it tries to average out the exposure across the image. The result is an overexposed light/white flower and an underexposed background. One way to get around this, is, assuming you are shooting in Aperture Priority, to set an exposure compensation of somewhere between -1/3 to -1 stop. You may have to experiment a bit to find out exactly what works.
You can see that you get more detail in the second image because you are shooting a darker flower against a dark background, so while the camera may try for the "18% thing", the darker flower does not get blown out and you get some more detail in the petals that you did not get in the images with the white flowers. Also, are you shooting raw? If you are then okay, if you are not, then I would encourage you to try it as you can do a lot more "correction" in post-processing with a raw image than you can with a jpg.
You can find a lot about flower photography on the web by searching for topics such as "flower photography" or "flower photography tips and techniques". For example, Ron Bigelow has a three-part series on Flower Photography on the web. The first one is here -
http://ronbigelow.com/articles/flowers-1/flowers-1.html. The second and third ones are found by following the links at the end of each subsequent posting. As well, you may wish to explore some of the images in Denise Ippolito's gallery as well as other parts of her web page -
http://deniseippolito.com/flower-gallery-2/.
I hope this helps a bit.
WesternGuy
