My pump seems to have not good suction, should I buy new pump ? Or change the parts? Using spectra 9+

Maybe check your valve? If you're using the original spectra valves, check for tears, cos they affect the performance alot. And the original spectra ones are so fragile. You can try changing to the medela valves. They fit my 28mm perfectly. Although they are more expensive than the spectra ones, they are more durable. :)