Learn Croatian: Žao mi je, nemam vremena. - I'm sorry, I don't have time.

In Croatian, you do not translate I am sorry word-for-word. Instead, you use this set phrase which literally means It is a pity to me. Žao means pity or sorry, mi means to me, and je means is.

Why is nemam written as one word instead of ne imam?

The verb imati (to have) is an exception. When making it negative, the word ne (not) merges with the verb to form a single word: nemam, nemaš, nema, and so on. For most other verbs, the ne stays separate.

Where is the word for I before nemam?

In Croatian, the ending of the verb already tells you who is doing the action. The -m at the end of nemam means I, so you do not need to add ja (I) unless you really want to emphasize it.

The dictionary says time is vrijeme. Why does it change to vremena here?

Two things are happening. First, the word vrijeme has an irregular spelling shift in its other forms, changing its core part to vremen-. Second, when you say you DO NOT have something in Croatian, the thing you don't have is usually put in the genitive case. So, vrijeme becomes vremena.