What should I do about the problem of not getting good grades in my studies, even though I study, memorize, and rely heavily on Allah, while the fear of the university system remains?

Ease your fear of the exam and plan well. Seek help through prayer and supplication. Read the question carefully and understand it thoroughly, then answer it. Seek Allah's help and ask Him by His Greatest Name to grant you success in your answer. Then leave a space and supplicate frequently. Know that whoever perseveres in acts of obedience and remembrance, Allah will suffice them in all matters, including: reciting the Mu'awwidhat (Surahs Al-Ikhlas, Al-Falaq, and An-Nas) three times in the morning and evening, performing the Fajr prayer, performing four rak'ahs of prayer at the beginning of the day, and reciting: "Sufficient for me is Allah; there is no deity except Him. On Him I have relied, and He is the Lord of the Great Throne," seven times in the morning and evening.