Learn Turkish: Nehirler genellikle göllere su taşır. - Rivers generally carry water to lakes.

The verb comes from taşımak (to carry). The root is taşı-, which ends in a vowel. To make it the Aorist (Simple Present) tense for general facts or habits, we just add the suffix -r, making it taşır.

Since nehirler (rivers) is plural, why doesn't the verb have the plural suffix -lar (taşırlar)?

In Turkish grammar, if the plural subject is non-human (like rivers, animals, or objects), the verb is usually written in the singular form. That is why we use taşır instead of taşırlar.

Why doesn't su (water) have an accusative suffix here?

Because it is a general, indefinite object. The rivers are carrying water in general, not a specific body of water. When a direct object is non-specific (meaning you wouldn't say 'the water' in English), it stays in its bare dictionary form.

What are the suffixes attached to the word göllere?

It breaks down as göl (lake) + -ler (plural suffix) + -e (dative case suffix, meaning 'to' or 'towards'). Together, they mean 'to lakes'.