If we wanna know God well, I think the first we should know His words well, and build a Good relationship with Him, so please help me.
what‘s the Bible verse you mean? could you tell us
Good question! Answer: use scripture. Always use scripture to explain scripture. In this case, it’s easy because all you have to do is read a few more verses.
Romans 9:18-24 New American Standard Bible (NASB)
18 So then He has mercy on whom He desires, and He hardens whom He desires.
19 You will say to me then, “Why does He still find fault? For who resists His will?” 20 On the contrary, who are you, O man, who answers back to God? The thing molded will not say to the molder, “Why did you make me like this,” will it? 21 Or does not the potter have a right over the clay, to make from the same lump one vessel for honorable use and another for common use? 22 What if God, although willing to demonstrate His wrath and to make His power known, endured with much patience vessels of wrath prepared for destruction? 23 And He did so to make known the riches of His glory upon vessels of mercy, which He prepared beforehand for glory, 24 even us, whom He also called, not from among Jews only, but also from among Gentiles.
Hope that helps.