Learn Hardcore Russian: Мой друг открывает магазин.

Мой means "my" and shows that the friend belongs to or is associated with the speaker. It is in the masculine singular nominative form because it agrees with друг (friend), which is a masculine noun.

Why is the verb открывает in the present tense used here? Does it mean my friend is currently opening the store?

The present tense in Russian can describe actions happening right now, habitual actions, or even near-future plans, depending on the context. In this sentence, открывает indicates that the friend is either in the process of opening the store or it is a planned action. Context usually helps decide whether the focus is on an ongoing action or a scheduled event.

Which case is магазин in, and why does it not show any distinct ending?

Магазин functions as the direct object of the verb and is in the accusative case. However, for masculine inanimate nouns like магазин, the accusative form is identical to the nominative form. That is why its ending remains unchanged.

How does the verb открывает agree with the subject друг in this sentence?

The verb открывает is conjugated in the third person singular form, which correctly agrees with the singular subject друг. This subject–verb agreement helps clarify who is performing the action.

Is the word order in the sentence similar to English, and can it be rearranged in Russian?

Yes, the sentence Мой друг открывает магазин follows the Subject-Verb-Object (SVO) order, much like English. However, Russian is flexible with its word order due to its case system; even if you rearrange the words for emphasis, the case endings (or lack thereof) on the nouns indicate their grammatical roles, keeping the meaning clear.