It is S70. When I drive on a bad road, there are knocks from under the car.
I checked the suspensions and they are functioning properly.
What can I check and how?

Check the front upper spring seats.Get a 13/16 wrench and try to turn the top nut under the hood for the front struts.If it turns it is bad.
Also the front sway bar links might be bad.

Is it better to get struts and susppention from the dealer or after market. What brand is better for S70

You can go aftermarket for the struts them selves or the links.
Im not sure if the spring seats are avalible aftermarket yet.

Thanks,
I got Sensa Trac Struts.
The noisy part was the Sway bar link to the struts.
Thank you for the advice.
Belle Tire replaced the Struts and charged labor only $60 for two. Alignment is separate. They did a good job

Cool im glad you got it fixed.