"Hij was ademloos toen hij haar zag."
Translation:He was breathless when he saw her.
I am confused when to use "toen" as while and when to use it as then. xD
When you use "toen" as then, your talking in the past tense. If you use "toen" as while, you use the past present. You can also use "toen" as when, like in the sentence "Toen ik je zag", what "When i saw you". But, you don't use "toen" as when if you are making a question such as "Wanneer gaan we eten"(When are we going to eat). Hope you are less confused now!