I really need help. I’m not able to be concentrate on anything, especially prayers. I always have negative thoughts about everything, even when I’m praying. And I don’t only think negative, my thinking is actually bad. I believe in Allah (swt) and I know that He will always answer my prayers when I truthfully ask Him, but I’m not even able to ask Him to help me. I feel that I’m lazy to even ask Him anything. My exams are approaching and I know that I’m not making enough Doua. When I pray, my mind is always somewhere else.

I don’t know how be concentrate when doing anything, and how to remove all those negative thoughts from my mind.

Try to be in the state of the wudhu all the times and read following Aayat after the iqamat before takbeeratul Ehram which helps you to concentrate in prayer kindly read the translation
Holy Quran 6:162
‎قُلْ إِنَّ صَلَاتِي وَنُسُكِي وَمَحْيَايَ وَمَمَاتِي لِلَّهِ رَبِّ الْعَالَمِينَ

Say, “Indeed, my prayer, my rites of sacrifice, my living and my dying are for Allah, Lord of the worlds.