I can't help you with technical issues beyond saying you should use an official copy from dlsite and start the game using start.exe, not start.swf.
To give her water:
1. Screenshot 1: Go to the room with the water/bread behind the glass door. Click on the white text in the red box to unlock the dialog option, then click on the green circle with blue button (see blue box). Once it zooms in, click on the green circle until it makes one full circle (should be 4 times, with the blue button back on top). The glass door should open.
2. Click on the bread, then click on the water. When you click the water, it should show screenshot two. Choose the option in the red box on the right to keep the water to give to the heroine.
3. Go back to the heroine and choose the talk option (top right) in screenshot 3. This should give you a number of topics to talk to her about, which are mentioned in the guide I linked.
4. To give water, you need to already have talked to her about food (you already selected the 食事について option in the top right). If you talk to her again, the 食事について option should be replaced by an option to give water in the top right. See screenshot 4.
5. You can only collect water/bread once per day. You can check the day by looking at the number in the top left of screenshot 1 (1日目 is day 1). The number underneath the day is the number of actions you have remaining in the day (行動残: 11 is 11 actions), which is the number of times you can move between rooms. To get to the next day, just move between rooms until the day changes.
