"I have chosen what I need."
Translation:Ik heb gekozen wat ik nodig heb.
That's a good question and rather confusing when you're learning Dutch I'm sure. As a native Dutch speaker, I'm going to guess the second 'heb' comes at the end of the sentence, instead of before 'nodig' because there already is a main verb in this sentence, also 'heb' in this case. It would be the same if I said: Ik eet wat mijn lichaam nodig heeft (I eat what my body needs). Another couple of examples: Wij kopen alleen kleding die we nodig hebben (We only buy clothes that we need), Jij bent gekomen omdat ik je nodig heb (You came because I need you), and lastly, Ik heb nodig wat ik nodig heb (I need what I need). I hope this sort of clarifies the grammar issue for you, but I'm sure there are other native Dutch speakers who can explain the grammar behind this better than I can.