What is the logic of asking a question?

Hello. I noticed that i can’t understand how to ask correctly in English.(I don’t mean easy questions)

Sometimes there are two verbs in a sentence and I can’t digest which verb the question belongs to.

For example;

1-) When do you think to go on a holiday?

What does it mean? Does it ask when to think about holiday or when to go?

And What is the rule here? According to what?

Because I can say: “I usually think about holiday in the winter months and search some hotels for a better holiday and decided when to go and where to go”

Or I can also say: “I think that I will go on a holiday next month.”

I mean, Does it ask the time of thinking or Does it ask the time of holiday? It’s a boring problem for me.

Let’s see another one.

2-) When did you decide that we will meet?

What must my answer be?

I decided yesterday that we will meet

or

I decided that we will meet tomorrow.

Which one and why?

3-) (We’ve talked about it here but I can’t still understand why.)

Where do you want to buy a book to read?

There are two verbs in one sentence and how do you all decide Which verb “where” must belong to? Are there any rules about how to understand easily? Thank you so much..