How to execute multiple / parallel tests and sequential tests in the same testrun

Hello guys.
In my testsuite I have a lot of testcases which can be executed at the same time. Only a few of them needs to be executed separately, because they would have impact to the other tests.

In the end I need 3 chunks. 2 chunks are running at the same time and after them the third chunk will be triggered.

How can I achieve this?