In english there are the simple, continuous, perfect, and perfect continuous forms of the past present and future tenses. 

Examples:

simple past: "I ate pizza"

continuous past: "I was eating eating pizza..."

perfect past: "I had ate pizza..."

perfect continuous past: "I had been eating pizza..."

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simple present: "I eat pizza."

continuous present: "I am eating pizza."

perfect present: "I have eaten pizza..."

perfect continuous present: "I have been eating pizza..."

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simple future: "I will eat pizza."

continuous future: "I will be eating pizza..."

perfect future: "I will have eaten pizza..."

perfect continuous future: "I will have been eating pizza..."

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I get that Dovahzul isn't a code for English, so what are the tenses of verbs in Dovahzul and how do we express them?

You can find a fairly complete list here.

There are some tenses that aren't going to translate well to Dovahzul, in particular continuous. Like German, Dovahzul simply doesn't have continuous tense.

The passive voice is also difficult to express because it's hard to distinguish it from the perfect (since lost is both "have" and "was").

paarthurnax

You can find a fairly complete list here.

There are some tenses that aren't going to translate well to Dovahzul, in particular continuous. Like German, Dovahzul simply doesn't have continuous tense.

The passive voice is also difficult to express because it's hard to distinguish it from the perfect (since lost is both "have" and "was").

Couldn't that be fixed? If it is so confusing, that could be an advantage of a constructed language, why not corect it?

That's a possibility. However, out of respect for the language, I'm inclined to disagree. While I understand that it is a constructed language, and that we have added a great deal to it, I don't think that we should necessarily change the way the language works to make it more familiar to us. 

Not only that, but when you think about it, it really isn't so strange that a language born from an immortal people where time is an abstract concept would not communicate the idea of time in such a uniform and finite way as we do in English. There's bound to be differences, as in any translation between two drastically different cultures. Time is completely different to the dov; it's like they can see a whole rainbow of colors that we can't. Imagine the difficulty in trying to describe those colors to we joor meyye. Vomindoraan.

@Aaliizah True, but I was referring to verb tenses specifically in dovahzul as in what is there. if time is abstract in concept yet finite in perception then have a construction that while using words that we have yet could be in dovahzul but translated into concepts that are forein