As your internship will be 12 EC you will need to gather another 18 EC through electives.
Below you'll find a few advised schedules, which should not cause a delay in your study programme.
2. Part time and full time combination
Choose two electives in period 1 and one in period 2. This way you can do you internship part time in period 2 and full time in period 3.
Disadvantage is that your internship will be interrupted by the holiday season and it overlaps with the 'end of year' rush.
3. Full time 1
Start your internship in summer and finish it end of period 1.
Disadvantage might be that your company coach is on holiday the first weeks of your internship...
4. Full time 2
Choose two (or three) electives in year 2. A third elective can be taken in period 3 of year 3.
Now check out the specific UvA job board with pre-approved internships