Thinking in Dutch — internal monologue in the target language — is one of the strongest indicators of language internalization, and also a technique you can deliberately practice. When fluent bilinguals describe their experience, they often point to the moment when they started thinking in the new language as the breakthrough point. You can accelerate this by deliberately narrating your thoughts in Dutch during everyday activities.
Start small: narrate a single daily activity entirely in Dutch. While making coffee: Ik pak de koffiemachine. Ik doe er twee lepels koffie in. Ik zet hem aan. Nu wacht ik tot de koffie klaar is. (I grab the coffee machine. I put two spoons of coffee in it. I turn it on. Now I wait until the coffee is ready.) The narration forces you to notice vocabulary gaps (what is the Dutch word for “coffee grounds”? — koffiedik) and provides natural topics for subsequent vocabulary lookup.
Advanced thinking practice: when you have a thought in your native language, immediately try to rephrase it in Dutch. If you cannot, note the gap and look it up. Over time, the Dutch phrasing comes first for certain topics — particularly topics you have been exposed to most in Dutch. Dutch thinking is particularly strong in learners who keep Dutch journals, speak with Dutch partners regularly, or work in Dutch-speaking environments. It is a sign of progress, not a prerequisite.