Learn Turkish: Tren yarın sabah merkeze varacak. - The train will arrive at the center tomorrow morning.

The root of the verb is var (to arrive). Because it ends in a consonant (r), we don't need the buffer letter y. We simply look at the last vowel (a) and apply 2-way vowel harmony, adding the future suffix -acak. Since the subject is the train ("it"), no personal suffix is needed at the end.

I thought "var" meant "there is" or "there are". Why does it mean "arrive" here?

You are right that the word var is famously used to mean "there is" or "there are". However, var is also a verb root meaning "to arrive" or "to reach". You can easily tell it is a verb here because grammatical suffixes like the future tense (-acak) can only be added to verbs!

The English translation says "at the center". Why does Turkish use "merkeze" (to the center) instead of "merkezde" (at the center)?

In English, we say we arrive "at" a place, treating it as a static location. But Turkish logic focuses on the motion of getting there. The verb var (to arrive) requires the dative case (the "to/towards" direction suffix). So we add -e to merkez, making it merkeze.

Can I say "Yarın sabah tren merkeze varacak" instead?

Yes! Both are perfectly natural. Time expressions like yarın sabah (tomorrow morning) usually go either at the very beginning of the sentence or right after the subject (tren). Putting the subject first just slightly emphasizes that it is the train (and not a bus or a car) doing the arriving.