Hello Dino and welcome to Writefix!

There is / there are

You can usually omit these words - they often don't add anything to a sentence. In your example, you already have a verb:

However, there are other developing countries had never used the financial assistance because it end up being corrupt by politicians.

Here's the sentence with a couple of other changes:

However, other developing countries have never used financial assistance because it ends up being embezzled by corrupt politicians.

Verb Tense

Watch out for verb tense - stay in one or the other and try not to change too much.

Some poor countries are being ruled by corrupt politician, who used the money for personal needs. In addition, when developed countries sent food supplies the convoy are being harsh. For example in Somalia, United Nations food supplies convoy are being attacked by rebels which the food supplies never reach to the people, who badly needed this help

Here's a rewrite with fewer tense changes. I've made some other changes, especially with the word 'harsh'

Some poor countries are being ruled by corrupt politicians, who use the money for their personal needs. In addition, when developed countries send food supplies the convoy are often attacked. For example in Somalia, United Nations food supplies convoys are being attacked by rebels, so the food supplies never reach the people, who badly need this help

Try to avoid making lists. Your third paragraph has some problems with comma splices:

There are many ways to help developing countries to eliminate poverty. Building infrastructure managed by international watched group, in this matter it helps to stop politicians corrupting the funds. With this type of organization, poor countries will definitely develops their economy, education and health system because funds are being spend for the right directions. Furthermore, lessen the tariff fees for poor countries when exporting their products to a develop countries, in this way, it helps local investors to gain more profits and improve the quality of their products.

One way to rewrite this could be:

There are many ways to help developing countries to eliminate poverty. One way is to build infrastructure using internationally monitored contractors. This will help to stop politicians stealing funds. With this type of organization, poor countries will definitely develops their economy, education and health system because funds are being spend for the right directions. Furthermore, rich countries could lessen the tariff fees for poor countries when exporting their products to developed countries. In this way, local investors will gain more profits and improve the quality of their products.

Overall, your essay is well organized. The last sentence in your conclusion is a bit general - it was as if you had got fed up and just wrote something to finish the essay!