Two teachers are teaching together, but only 3 times per week out of 5 lessons (lessons with assistant)

You can input this exactly as is requested, so - create
lesson with one teacher - two times per week
AND
lesson with two teachers (via "More teachers" button) - three times per week See: How can I create co-teached lessons

In timetable you can see two colors on cards with two teachers and two different rows in class contracts from the same subject.

Notes:
- if you use the same subjet in both lessons, then the software automatically tries to distribute these 5 lessons equally over the week, in this case one period per day.