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Yes, this is correct. This article will help you with saving your geraniums over winter: https://www.gardeningknowhow.com/ornamental/flowers/geranium/how-to-save-geraniums-over-the-winter.htm

If you do not put your geraniums into dormancy for the winter, then you can prune geraniums in late fall or just before you bring them indoors. Prune them back by 1/3 to 1/2, focusing on stems that are woody or leggy.

These articles will help: https://www.gardeningknowhow.com/ornamental/flowers/geranium/how-to-save-geraniums-over-the-winter.htm
https://www.gardeningknowhow.com/ornamental/flowers/begonia/wintering-begonias-overwintering-a-begonia-in-cold-climates.htm

Yes, you will water during the winter, but much less than when the plants were outside growing. Water enough to keep the soil from getting completely dried out. Check the soil weekly with a moisture meter, or long dowel or kebob skewer, inserted all the way to the bottom of the pot. Don't water until the meter reads about 1/2 way between dry and moist; the tester should feel very slightly damp between your fingers

Alsace is perfect for geranium growing - exactly the right amount of light, moisture, and temperature. There are hundreds, if not thousands, of geraniums varieties available. If you used the exact ones they use in Alsace, that's no guarantee you'd get the same results. You need to use the varieties that do best in your area. For this information, it's best to go to a knowledgable plant or nursery store for advice, or your local Master Gardeners association. They have loads of information and assistance available for home gardeners. This link will help you locate the nearest group:

http://mastergardeners.org.uk/get-involved/find-your-nearest-master-gardener/

Here's a quick primer in growing geraniums: https://www.gardeningknowhow.com/ornamental/flowers/geranium/geranium-care.htm

This article may help: https://www.gardeningknowhow.com/ornamental/flowers/geranium/leggy-geranium.htm