well I am the one who have planned to move to Poland to learn polish language and then start working as I have got a lot of good offers to work at some good companies as IT engineer
As far as opportunities for job advancement and future earning potential in terms of how much absolute dollars you can save up per month, your options as an IT engineer are much better in a northern Western European country or in the Anglosphere (US, Canada, Australia and NZ) than in Poland. IT engineering jobs in Poland are often outsourced from these countries specifically to save money on wages, with the real good, interesting and high-paying jobs remaining in the home countries. You are likely to quickly hit a barrier that prevents significant upward advancement, unless you have some serious qualifications in management or finance, as well.
As for learning Polish, it is unlikely that you will develop fluency to the level that you will be able to compete with native Poles on the job market for about five years, at least. You would have to possess some serious qualifications in areas highly in demand to make a go of it until then.
I'm curious what you consider "good offers to work". How much have you been offered?
my question is WHY
The lack of well-paying jobs, especially for educated young graduates entering the market, is a major problem. Low wages even for established workers is another. Poor quality of university education is a third. High cost of living in relationship to wages is yet another. Overall backwardness of the country in relation to its neighbors to the west is another. Not unique to Poland. Greece, Italy, Spain and Portugal share a lot of the same problems, and all of those countries are in the old EU. Poland has not been in the EU for a long time, only nine years. True, Poland is improving, but it still has a ways to go. Though no country is perfect, the overall quality of life is significantly higher in northern Western European countries and the Anglosphere than in Poland, and the higher costs are generally more than offset by the higher wages. While many Poles leave Poland to work in those countries, relatively few people from those countries come to work and live in Poland. For good reason.
Most poles that I chat with are sad and depressed of being in this country
Most Poles are appear sad a depressed, even when they move abroad. In Poland, there is a sort of taboo against demonstrating that you are happy in public, and that is deeply ingrained. I've been living in Poland for eleven years, and I have learned not to smile constantly from ear to ear like an American. Just today, when I was walking through town for a meeting, a random guy come up to me and complemented me on my long white beard. That put a big smile on my face, which lasted no more than 30 meters before I realized that people were staring at me because I was smiling so openly.
I mentored a teenage student for ten hours a week for five years, and in those approximately 2500 hours, he never laughed. Never. Not even once. The most I could get out of him was a brief, faint sort-of-smile. And his family was fabulously rich, even by American standards. It's different in private, with people you know. I mentor four other boys, all of whom are all smiles and giggles when we are alone. But when they leave the house, they put on their serious-looking "street face", and their reactions to my jokes are much more subdued.