Why are animals so weak against environmental change compared to humans (no matter if it's a desert, jungle or city, the human will always adapt to its environment)?

Humans don't adapt well on their own, they are just good at building artificial things to help them adapt. A human will be inferior in the desert compared to desert-specialized animals but (as a group) has ways of building shelter, drilling a well to find water ... Humans will freeze to death in winter unless they build themselves houses with heating (or at lest keep a fire going in their cave). Some will even fail at the simple task of walking barefoot across a rocky field.

So, humans compensate for their weak adaptation by building tools, which allows them to become more universalist than many other species.

What is the best way to build up strength for combat sports?

If by "combat sports" you mean anything where direct physical contact is the norm (which could include boxing, martial arts, mixed martial, other fights, together with collision sports including American football and rugby) my suggestion would be to speak to coaches about these various sports.You mention building strength, so strength is typically specific to a sport rather than

Why is there so much sugar in yogurt?

Yogurt had never had sugar in it, since Turkish nomads first fermented it. That was only until it met sugar-lover Joe.Dear Americans, please stop putting that sh*t into our delicious sour yogurt. Respect its nomadic soul.Additional advice: Also instead of sugar-addicting soda/cola, try drinking "Ayran" the yogurt drink. Drink it cool and with some fresh mint. There is

Is 340 push-ups every two days good for a 12-year-old?

it is not good to force a pushup when you feel the pain in your muscles. But for example if you make ten .twenty or thirty pushups and then rest for a while until you can feel the strenght coming back and you feel you can do more and again you do twenty or thirty