Learn Hardcore Turkish: Sınav öncesi ders çalışıyorum.

It means "before the exam". The noun sınav translates as "exam", and öncesi (derived from önce, meaning "before") creates a phrase that specifies the time period leading up to the exam.

How is the subject I indicated even though it isn't explicitly written?

Turkish often omits subject pronouns because the verb conjugation carries that information. In çalışıyorum, the ending -um shows that the verb is in the first-person singular form, clearly meaning "I am studying."

What is the role of the -yor suffix in çalışıyorum?

The -yor suffix is used to form the present continuous tense in Turkish. In çalışıyorum, the verb root çalış- (meaning "to work" or "to study") combines with -yor and the personal ending -um, indicating that the studying is happening at the moment.

Can sınav öncesi be replaced with sınavdan önce? If so, what are the nuances?

Yes, both expressions can mean "before the exam". Sınavdan önce uses the dative case with önce (meaning "before"), whereas sınav öncesi is a compound phrasing that conveys the same idea. The differences are subtle; the compound form might emphasize a specific period or context leading up to the exam.

How are the different parts of the sentence connected in Turkish grammar?

The sentence is structured with a time adverbial phrase (sınav öncesi) at the beginning, followed by the main clause (ders çalışıyorum). Turkish word order allows such introductory phrases to set the temporal context without additional connectors, and the subject is embedded in the verb form, making the sentence both concise and clear.