Can I pray namaz while closing my eyes, and that is because of concentration in my namaz and nothing else?

Yes you can but as traditions says we should not close our eyes but even it would not invalidate your Namaz. Also for concentration in Namaz opening ones eyes doesn’t play any role you wann do it first try to find the meaning of Salat and logic and philosophy behind each and every action of Namaz. Try to concentrate slowly inshallah by the time you will get habit of it.