I have a hard time writing an introductions.

Or: "I'm having a hard time writing an introduction." Or have had, have been having. Depending on whether you want a habitual or a specific sense. If you wanted habitual, this is wrong; if you were just talking about this one introduction, it's merely a little unnatural.

It may be the hardest part of the whole thesis, yet it is one of the most important chapters, includingalong with Conclusion and Abstract.

"including" here sounds like Conclusion and Abstract are part of the introduction, like it includes them. You'd maybe say something like "it's one of the most important chapters, which include". Well, you might say that if this was part of the thesis. In regular speech it'd be a bit odd.

It's a technical thesis, so don't worry, if you don't know what it all means.

Gesture recognition is one of many challenging tasks in image processing that hasve found applications in manyvarious industries.

It's the tasks that have found applications, so plural. Or: "one of many challenging tasks, one that has found".

It is vital in the automotive industry, home automation, and healthcare, and pivotal to human-computer interaction, such as augmented reality.

Pivotal is very nice!

Most of them, however,However, one commonality is that most techniques rely on hands' key points represented in a 3D coordinate system.

Original sentence was fine but I'd like to justify the "however" more, make the contrast more explicit. So there's one suggestion.

The boom in machine learning and, specifically, deep learning opened the door to many complex tasks that would hardly bebe very difficult to solved with algorithmic approaches, especially tasks in image processing such as gesture recognition and hand pose estimation.

"would hardly be solved" - would rarely be solved, very few people would solve, would only be solved very partially. Talking about the difficulty seems better. And "tasks ... such as image processing" makes it sound like image processing is one of the tasks to be solved, so I suggest making it clearer that it is a fruitful area rather than a task itself.

This work aims to develop a system that allows the user to set the desired gesture as they need and provides them with feedback on the gesture.

The system allows and provides.

Such features bring the need to create a slightly differentnecessitate the creation of a novel gesture recognition system, which canould be adopted in many applications, such as hand scanning.

"bring the need" strikes me as awkward, when you could show off "necessitate" :)

"novel", in my experience, is what academic papers say when they have created something slightly different.

And "could" just seems to fit better. Can't figure out an explanation why. I guess just because this feels more conjectural?

The latest methods, which can be employed on for addressing the above-mentioned tasks are introduced in Chapter 2, which provides a thorough introduction to these methoddiscusses their basic characteristics.

More natural. And I try to avoid repeating "introduce/introduction" and "methods", although I don't know if you actually discuss their basic characteristics!

They are described in greater detail in Chapter 3.

Perhaps "These" if you mean you only describe the methods that you use?

Chapter 4 presents an overview of the available datasets that may be employed toin training the introduced techniquesrelevant models, and describes the onesose used in this work more thoroughly.

Chapter 4 presents and describes.

Training is not, I think, something you would commonly to do a technique. In machine learning you train models and I'm pretty sure that's what you mean. It would perhaps bear some specific introduction, but you use "train" without introducing it and that's a machine learning word so maybe it's unnecessary.

The system's design is presented in Chapter 5, which focuses on connecting all three tasks.

Each task was evaluated separately, and the complete system was tested in real conditions, which iith results presented in Chapter 7.

Not sure if what you had was ungrammatical, but this makes the reader do less work.