Learn Turkish: Labirent şafağa doğru çok tehlikeliymiş. - Apparently, the maze was very dangerous towards dawn.

When used as a postposition meaning towards (for physical direction) or around (for time), doğru always requires the preceding word to take the dative case. Here, the target time is şafak (dawn), so we add the dative suffix -a to get şafağa doğru (towards dawn).

Why did the k in şafak change to a ğ in şafağa?

This is an example of consonant mutation, which you have seen before. When a Turkish word ends in p, ç, t, or k and takes a suffix starting with a vowel (like the dative -a), that final consonant usually softens. Here, the k in şafak softens to ğ.

How do we get was apparently from tehlikeliymiş?

The word is built from tehlike (danger) plus the adjective-forming suffix -li, making tehlikeli (dangerous). To say was apparently, we add the hearsay past tense suffix -miş. Since tehlikeli ends in a vowel, we insert the buffer letter -y- to get tehlikeliymiş.

Could I say tehlikeliydi instead of tehlikeliymiş in this sentence?