Hello Marica, my Adeniums are in semi-dormant phase right now. Though one is blooming while holding on to its leaves..the other one is not in bloom but still holding on to existing leaves. No new leaves being made, and some existing leaves are slightly turning brown, so I know both are in dormancy. The photos of the one in bloom posted earlier in this thread. I have mine by our south facing window, and really glad the sun is out, so it gets its much needed light and warmth.
That is typical of Adenium leaves when the are in dormant mode, leaves turning brown, but the caudex should stay firm, may shrink a bit but it should stay firm.
If your plant is still making new leaves, you can still lightly water, but not too much as what we do during the hot and dry months. I prefer to keep mine on the drier side. It is the height of winter, and light/heat intensity is still not at that preferred level it likes.