You can stop eating animals.
You can find an NGO and support their actions in this matter.
You can leave out a small fraction of your garden unattended, let it grow wild and it will attract many different species.
You can stop using chemicals when farming.

Yes, you can. If we eliminated all the chemicals and grew plants in an organic way and for people only, we might be able to do that. If we also stopped farming billions of animals solely for the purpose of them being killed and eaten by humans, we would increase our changes of going full organic.

For instance, there should be a fairly easy and user-friendly way (supported by the government as well) to implement systems on saving the used water and use it for flushing the toilets. A way fit for all the citizens so that the impact is greater.

The citizens are not as severely affected as the agriculture, birds, insects and most definitely, the plants.
The water is a very precious commodity, we're beginning to see that and we have to learn that very soon. There is an on-going drought in the country, it doesn't rain nearly as much as we were used to and there was almost no snow in the winter. The underground water levels are lowering, the above ground water sources are at a fraction of their capacity.
Everybody can do their bit. Install some water-saving enhancements, flush your toilet wisely and, generally, do not waste the water.

My local council is trying to mitigate the effects of the climate change in a few ways, but, this being in a densely populated area, they are limited.
For example, the council is planting new trees in the streets or lowered the incidence of cutting grass in public parks.

The benefits of a sharing economy are clear - saving the environment!

I have been using a car share a lot while living in the USA, this has been a perfect way how not to burden the environment with other emissions. And saving money, too:)

It was more alone then with others because of covid distance-requirements. However, we compared at the end the sacks filled with garbish --> it was a competition in the end :) Quite good fun, I think. And finally we all have a good feeling from a clean environment of the pond and forest nearby. Hope to repeat soon, some areas are really disgusting.

We stay at home because of grandma and other elder or immune-weak people. I would never threat people's health by my behavior. Therefore, it is important to connect with others and make them less nervous, scared or feeling lonely. As I am extrovert, I need to talk a lot and I am always pleased when someone calls me. So, I call other extroverts a lot to make them happy as well ^.^

The 7 Habits of Highly Effective Reusable Bag Users

1. Get bags that you like. I like canvas bags with sturdy straps.

2. Keep them where you'll see them. For me that means the back seat of my car, not the trunk. I also keep one in my bike bag.

3. Always bring at least one more bag than you think you'll need.

4. The minute you unload the bags, put them where you're likely to see them the next time you go out. I hang them on a door handle.

5. Wash your bags from time to time.

6. Forgive yourself when you forget to bring your bags.

7. Do not use your occasional failure as a reason to give up.