Questions & Answers about Þegar ég las gömlu bókina, var námið gott.
Why do we use þegar for "when" here instead of hvenær?
Þegar connects two parts of a sentence to say that something happened at the time of another event. You use hvenær only when asking a question, like "When did you read it?". Because this is a statement about a past event, we use þegar.
Why does the second half of the sentence start with var (was) instead of námið (the study)?
This happens because of the V2 (verb-second) rule. The entire first phrase (Þegar ég las gömlu bókina) counts as the first block of information. The main verb (var) must come right after it in the second position, before the subject (námið).
Why is "old" written as gömlu instead of the dictionary form gömul?
Because we are talking about a specific book (it has the "the" ending in bókina), the adjective must use its weak form. For feminine nouns in the accusative case, that weak ending is usually -u.
In English, "read" can be present or past tense. How do we know which one las is?
Unlike English, Icelandic has entirely different forms for the present and past tense of to read (lesa). The present tense is ég les, but the past tense is ég las.