Your have some grammar errors in this essay, but I would do some revision before I worried about that. Here are some pointers to help you get started.
I think you need to try and focus the introduction a little more. You start our saying, "we cannot deny" and finish with "I obviously disagree." I think you might be bouncing around a little too much here. The introduction should prepare the reader for the ideas you are going to be presenting. I would also leave out "for several reasons which will be analyzed in this essay." This is not a strong thesis statement. You do not need to say you are going to be analyzing the reasons. Instead, make a strong statement that summarizes the points you are going to be addressing. After reading your statement, the reader should already know that you are going to be discussing your reasoning in further detail.
The body of you essay has some great points, but I would try to expand on this a little by picking one more topic to discuss. Try to find another area you think government would be better off spending money on, and write a paragraph on it as well.
Furthermore, humankind has confronted with many problems such as diseases, disasters which need to be solved as soon as possible. Government should spend more money to improve health systems in order to upgrade living standard.
When writing a paragraph, you should think of the first sentence as a mini thesis statement. In this case, I think the second sentence better summarizes the paragraph.
The conclusion should be a paragraph that summarizes your arguments. You need more than one sentence to do this.
I think you are off to a great start, and you have some very interesting arguments. Once you do a little revising, I think you will have a much stronger essay, and then you will be ready to focus on grammar.