Questions & Answers about Við fundum lykilinn á endanum.
- Við = we
- fundum = found
This is the 1st person plural past tense of finna (to find). - lykilinn = the key
This is lykill (key) with the definite article attached, and in the form required by the verb. - á endanum = in the end / eventually / at the end
This is a very common Icelandic expression.
So the structure is basically:
Við + fundum + lykilinn + á endanum
We + found + the key + in the end