Hello Mohammed and welcome to Writefix!

The essay is OK in parts so I don't see why you shouldn't pass - it depends on the level you are at!

Introduction

Your introduction starts well, but the last sentence (the Thesis sentence -  the one which tells the reader what you are going to do) could be stronger.

There are three main causes for the huge increase in obesity percentage, and there are effects of that too.

The first part of the sentence is OK, but you could give the main causes directly. The second part is a little weak. You could write something like this:

The three main causes of the huge increase in obesity are X, Y and Z, and the problem has a huge effect on people's health, self-esteem, and the country's medical system.

Your thesis sentence would be like a signpost for the rest of your essay.

Word order, Word choice, Articles

• Obese people eat fast and oily food too much. ==> Obese people eat too much fast food and oily food.
• Walking problems are consequences of the lack in exercise ==> Walking problems are consequences of the lack of exercise.
• Furthermore, the obese person may feel depressed and sad because of his look ==> Furthermore, the obese person may feel depressed and sad because of his or her looks/appearance.
• Parents let their children eat what they want and not to offer a healthy food for them. ==> Parents let their children eat what they want and do not offer them healthy food
• The first cause for the obesity is the diet. ==> The first cause of obesity is a poor diet.
• The third factor is the absent of healthy food education.==> The third factor is the absence of education about healthy food.

Paragraph Two

These causes result in bad effects on the society and the individual.

Causes here is definitely the wrong word. You are in a new paragraph so it's better not to refer back to the previous paragraph by using a word like "These causes..." Let's change it completely...

Obesity has bad effects on the society and the individual.

Now the topic of your paragraph is clearer. The reader doesn't have to go back.

Conclusion

I would change the conclusion a little. It's a little repetitive -  it gives us information we have already. It's always hard to write a good conclusion but the main features are

• a summary with both sides (you've done this,but we need to use different words to avoid repetition)
• your opinion
• something about the future

Perhaps something like this might work:

Saudi Arabia faces a big problem with obesity as result of poor diet and a lack of exercise and education. Individuals and society are affected. Unless the government and individuals take steps to deal with this problem, the cost of medical treatment will rise and the quality of people's lives will suffer.

Make sure you don't use this paragraph on Monday!