drive belts (ex. serpentine,Service engine warning, MAF code and O2 sensor code, along with check suspension light are turned on

My car has an O2 sensor code on, MAF code as well as service engine warning. I had the sensor fixed. Also, I had the emissions tested along with the replacement of serpentine belts. The check suspension light is on occasionally. The car is very loud usually while idling. After all the checkups, the O2 sensor code is still on, the check engine light is on as well as the MAF code. Please advise me what to do next.