What is the ruling on bringing university degrees for individuals who studied laws that contradict the law of Allah, knowing that one of them is an infidel and the other said words from which that can be understood, and is bringing these certificates considered major or minor disbelief?

Your questions confirm that you are afflicted with waswas (obsessive whispering), and its only cure is to ignore it. Whoever indulges in waswas will be led into great evil by it. Occupy yourself with memorizing the Quran, reading books on spiritual edification (raqāʾiq), and stories of the prophets and the righteous predecessors (salaf al-ṣāliḥ). Know that declaring someone an infidel (takfir) is not a light matter, and one whose Islam is established with certainty is not removed from it by doubt. Scholars have mentioned that whoever commits an act that could be interpreted as apostasy or otherwise is not considered an infidel because of it. If there is even one way to keep a Muslim within the fold of Islam, then it should be acted upon. As for studying law, its ruling varies depending on the purpose behind it.