Why people waste of nature resources? how can i tell them to stop it?

The landlady’s kindness has nothing to do with being wasteful, except in the sense that your fellow students appear not to be mature enough to handle the freedom they are given by the landlady. They appear to still need a parent to tell them what to do. Write your parents a letter and thank them for doing a good job raising you because you are being responsible while living away from them.

As to your fellow students, set a good example, but you probably will not be able to influence your choices too much because having a peer lecture you is usually resented.

I agree with @PandoraBoxx . You can do your best to show them by example how to conserve energy, but as far as getting them to stop, the best you can do is ask them. Good luck getting them to listen to you.

Just come out and tell them, they might listen, they might not. But at least try.

As others say, lead by example.

There is only one person we can control, and that is ourself. However, perhaps it would be useful to print out some information about the importance of not being wasteful and post it on the bulletin board, or leave in a public place. Educating people about the issue is a good step to solving it.

Try to pursuade them.
Two reasons:

1) The landlady is likely to stop being kind if your flatmates abuse her trust. You’ll have to start paying for food, water, and energy.

2) It is important for the future of all humanity, and in particular, any children they may have, that we tread more lightly on the surface of our planet. If we use up all the fresh water now, our grandchildren may be parched and thirsty all the time. If we use up all the energy now, burning oil like there is an endless supply, we’ll use it up faster, and we’ll add to global warming.

You may also want to add a third reason: it hurts you when you see them being so wasteful and unkind.