"Zsuzsa is painting old department stores."
Translation:Zsuzsa régi áruházakat fest.
Why isn't "Old" pluralised here to become "Régiek"? For example "Zsuzsa fest régiek áruházakat" ?
Attribute adjectives are not made plural (just like in English): http://www.hungarianreference.com/Adjectives/absolute-adjectives.aspx
And oddly enough, the opposite of German :) There, predicative adjectives are not made plural or otherwise inflected, but attributive ones are.
fest is present tense: he paints, she paints.
festeni is the infinitive. You would use it in situations such as "can paint", "wants to paint", "likes to paint", etc., where there is an additional verb involved.
is it so much difference between üzletházak and áruházak ? üzletházak is not accepted
üzletházak are business - can be any sort. áruházak are large department stores that sell a wide range of goods and are usually bigger than (say) six normal businesses.