if you actually un-enrolled (officially withdrew from the school), you could say that you will re-enroll.
I took a break from university for 6 months to travel. I will re-enroll when I get back to my country.
If not (say you were on a leave of absence or sabbatical), you could say
I took a break from university for 6 months to travel. I will start back up again when I get back to my country.
or
I took a break from university for 6 months to travel. I will go back to school when I get back to my country.
Or, slightly more formally,
I took a break from university for 6 months to travel. I will resume my studies when I get back to my country.
This second suggestion is very similar to one of your ideas about how to express it. We don't usually talk about university as something one does, though. It is a place we attend, or go to, or it modifies some other noun. So your other suggestion could be modified to:
-"I am going to carry on with my university studies when I get back to my country."
-AmEng