Are they adjectival or adverbial?

Hello everyone.I have some sentences which I am not sure about. These prepositional phrases are adverbial or adjectival or both of them. 1-) The judge made a decision to arrest him."To arrest him" is defining "made" or "a decision". I think it should be "a decision" because What kind of decision is it? It is a decision to arrest him.But we don't have any answer to the question "Why did the judge make a decision?""to arrest him" should not be an answer to the question, because if it becomes an answer to the question,It means:"The purpose of the judge's making a decision/ the aim of the judge was to arrest him."And It is not what the sentence means. 2-) I have some doubts about you."About you" is defining "doubts" or "have" ? I think, It should be "some doubts". Because,What kinds of doubts are they? / Which doubts are they? They are some doubts about you.With the same idea,Why/how/where/when do you have? It doesn't make sense. We can not have any answer to these questions. 3-) We have enough money to be able to buy a new house."To be able to buy a new house" is defining "have" or "enough money" ?I think "enough money". We have an answer to the questions about money.But we don't have any answer to the question "Why do we have?" 4-) You should make a plan to discover Europe."a plan" or " make" ?I think, both of them are possible right now. Because, Why should you make a plan? In order to discover Europe.What kind of plan/ Which plan is it? It is a plan (in order) to discover Europe. Do you agree with me?