All of the normal modes are derived from the Major scale, where the tonic is a different degree from that scale. Your example concerns C Phrygian. Phrygian has the tonic derived from the third scale degree of Major, and C natural can only be the third degree of Ab Major, also known as Ab Ionian.
Think of the Ionian scale as its scale degrees:
Phyrgian has 3 as the tonic, so the scale would be shifted:
Here I wrote the chords out so you can see the difference compared to major. As you can see both Db and F are common between the Dbmaj7 and Ghalfdim7, with the Ab moving down a half step to G, C down a whole step to Bb, and the bass Db moving up an augmented 4th to G. The A4 is very important in a dominant chord in major, since the interval is rather dissonant and the notes are only a half step away from the tonic chord, as can be seen on the major side between F and B. B is pulled up to the tonic while F is pulled down to the third of the tonic chord. This interval is also only present between 4 and 7, which in Phrygian is now 2 and 5.
Next the bass moves up a perfect 4th to the tonic, C, making a nice cadence, while the soprano moves down a half step taking advantage of that flatted second degree half step which wants to resolve to the tonic. F moves down a whole step to Eb instead of a half step, so it's not quite as nice, and Bb and G stay the same.
When writing in modes it's best to take advantage of it's unique properties compared to its relative Major or Minor scale. Half steps tend to want to resolve the most and sound great doing so compared to whole steps. There are also many ways to voice the chords and lead the voices depending on what intervals you wish to focus on. In my example, if you added a Db to the V chord an octave lower than the soprano the augmented 4th between G and Db adds extra tension. Db is the unique tone in Phyrgian, and both the II and v chords have it, making them great chords to works with.