Learn Dutch: Jouw vader is altijd erg streng. - Your father is always very strict.

Jouw is the possessive pronoun meaning 'your', and it is used when you want to put a little extra emphasis on whose father it is. Je is also correct and much more common in everyday speech. Jou (without the w) is the object pronoun meaning 'you', so it cannot be used here.

The word erg means 'bad', right? Why is it translated as 'very'?

You are right that erg can mean 'bad' or 'terrible' on its own. However, when it is placed directly before an adjective like streng (strict), it acts as an intensifier meaning 'very'. You could also use heel here: heel streng means exactly the same thing.

Why doesn't streng get an -e at the end?

Adjectives only get an -e ending when they come directly before the noun they describe (like de strenge vader). In this sentence, the adjective comes after the verb is, so it stays in its basic dictionary form.

Could I change the word order and say is erg streng altijd?

In Dutch, time words like altijd (always) usually come as close to the conjugated verb as possible. Because of this rule, altijd steps in right after the verb is, pushing the descriptive words erg streng to the end of the sentence.