Is it good/permissible to make a deal with Hashem?
Example: “I will learn an hour every shabbos for a month if I get above a 90 on my exam tomorrow”
We don’t make deals with Hashem, with the exception of the mitzvah of giving tzedakah. What you may do is to pledge (bli neder) to learn an hour every shabbos for a month, and daven that in that zechus, Hashem should help you get a good mark on your test.
Devorim 6-16, Tractate Ta’anis 9a, Sefer Hachinuch 395.