Hello Sophia and thanks for this essay.

Introduction

How could you make your thesis sentence more specific to your essay? At the moment, you could use it in any essay. This could be regarded by IELTS examiners as “memorized chunks”  of text, and penalized with weaker candidates, or omitted from the total word count. In your case however, you clearly are able to write very well, so you don’t need to rely on these.  Have a look at this discussion on memorized chunks at raoulschinasaloon.com

In this essay, I will explore aspects of this issue and finally present my own perspective.

This could be rewritten as

In this essay, I will explain why experiencing and learning from the local culture can result in more memorable travel.

You have very good examples in Paragraph 2. The word ‘abiding’ in the last sentence of Paragraph 2 needs some work , and the reference at the end (‘this intention’) could be clearer.

Perhaps abiding by local inhabitants may ensure the fulfillment of this intention

This could be rewritten as

Living for a short while with local people can allow us a glimpse of exotic cultures and different lifestyles

However

Be careful with ‘however’ and 'nevertheless' - don’t use them to join two parts of a sentence. The result can be a comma splice or a run-on sentence.

Medical knowledge is improving at a fast rate, however there are still many diseases that cannot be cured…

Just use a full stop (easiest!), or a semicolon:

• Medical knowledge is improving at a fast rate. However, there are still many diseases that cannot be cured…
• Medical knowledge is improving at a fast rate; however, there are still many diseases that cannot be cured….

The argument may be true to some extent, however, a fact may be neglected that an expensive international trip is intended for pleasure rather than cultural spread.

I would remove the passive, remove the backward-looking reference (“the argument”), remove the generalization, and change the punctuation:

It’s true that diversity can be fascinating. However, we need to remember an expensive international trip is often intended for pleasure rather than for spreading cultural awareness.

Thanks for another very good essay!