Learn Turkish: O mağaza hem büyük hem pahalı. - That store is both big and expensive.

Hem... hem... is a pair of words used to mean "both... and...". You place hem right before each of the words you are connecting. In this sentence, it connects two adjectives: büyük (big) and pahalı (expensive).

Where is the verb 'is' in this sentence?

In Turkish, you don't always need a suffix or word for "is". For the third person (he/she/it or a noun like "that store"), the "to be" meaning is usually just understood from the context. You could add the suffix -dır at the end to make it pahalıdır, but in everyday speech, it's very common to leave it out completely.

Does 'o' mean 'it' or 'that' here?

Here, o means "that". While o is the pronoun for "he/she/it", it also acts as a pointing word meaning "that" when placed directly in front of a noun. Because it comes right before mağaza (store), it means "that store".