Learn Turkish: Mühendis bilgisayardan sunucuya veri aktarır. - The engineer transfers data from the computer to the server.

The root of the verb is aktar- (to transfer). According to the aorist rules, verbs with more than one syllable that end in a consonant take the 4-way vowel harmony suffix -Ir (-ır, -ir, -ur, or -ür). Since the last vowel in the two-syllable root aktar- is 'a', it takes -ır. (Single-syllable roots generally take -ar or -er).

Why is veri not written as veriyi if it is the thing being transferred?

Because the "data" here is general, not specific. If the sentence meant "transfers the data" (a specific file we already know about), it would take the specific direct object (accusative) case and become veriyi. Since it just means transferring "data" in general, it stays in its plain dictionary form veri.

What does the -y- do in sunucuya?

The word for server is sunucu. To say "to the server", we need to add the "to/towards" suffix (the dative case), which is -a or -e. Because sunucu ends in a vowel and the suffix is a vowel, we must use the buffer letter -y- to separate them, giving us sunucuya.

How do we know the transfer is "from" the computer?