"There are also banks and stores in the big buildings."
Translation:A nagy épületekben bankok és üzletek is vannak.
I haven't understood by now is the word order in Hungarian as strict as in English, or is it flexible? Should the verb always be in the end of the sentence?
The stressed, most important word (or the one that answers a question that has just been asked) always comes right before the verb.
The verb does not have to come at the end.
For example, the following two orders are both fine. They both stress fiúk (you're trying to tell the listener WHO is studying):
A fiúk tanulnak most.
Most a fiúk tanulnak.
The following two orders are also both fine. They stress most (you're trying to tell the listener WHEN the boys are studying):
A fiúk most tanulnak.
Most tanulnak a fiúk.
Putting the verb right at the beginning of the sentence would tend to stress the verb itself. So the following sentence is also fine:
Tanulnak most a fiúk.
"Bankok és üzletek is a nagy épületekben vannak". Is the word order wrong in my answer? (it was rejected)
It's.. weird, at least. If you have nouns that are not preceded by an article, you should place them in the focus position, i.e. in front of the verb. You may say "Bankok és üzletek is vannak a nagy épületben."