Difference between 决策 and 决定
决策is a noun and can only be used as a noun
for example 这是一个非常重要的决策。this is a very important decision.
决定 is a verb but also a noun
verb example 你要决定你想去哪。you need to decide where you want to go
noun example 这是老板的决定，不是我的。this is the boss's decision, not mine.
hope this helps.
P.S. I am Chinese.