We're do I get health certificate to apply for visa

You don't need life insurance - do you mean private health insurance (which you do need)?

For private health insurance you need a policy that is compliant with the visa requirements (including no 'co-payments'), which many companies will offer. You also need to pay upfront - i.e. not by monthly direct debits. I would recommend shopping around, as prices vary widely. I am with Sanitas (part of the BUPA group), and I have also seen DKV recommended on this forum.

The medical certificate needs to be obtained from your doctor - most doctors will do this and normally make a small charge to do so.

Hope this helps!